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Friday, February 03, 2023

2d10 Combat

Many RPGs center around combat, so it's important to get it right. So I think my combat is going to blend ideas from Pathfinder 2e, D&D 5e, and Warhammer: Age of Sigmar Soulbound.

Actions

The main idea I'm borrowing from Pathfinder is the idea of actions. Every player gets three actions. Everything they can do uses those actions. Some things--movement, attacks, a few non-attack spells--take one action. Other things, like loading a crossbow, or casting most spells, can take two or three actions. Some things--for  example, certain powerful spells--could take up to 6 actions, and have to be split between turns.

In addition, players get a reaction each round. The reaction works for opportunity attacks, and other things that only take a single action. This way you can ready an action--spend an action on your turn to set the conditions to trigger an action.

Pathfinder 2e uses penalties to make it difficult to make multiple attacks on your turn. You can use two actions to make two attacks, but the second attack has a -5 penalty. If you use a third action to make a third attack, you take a -10 penalty. I don't really care for this, and would probably use something like D&D 5e's Extra Attack feature. You can only make one attack during your turn unless you have an ability that lets you make an extra attack. And that includes spell attacks.


Damage by Degree

When you hit with your weapon, the damage will be a base amount (based on 0-5 for your weapon + Fortitude) times the number of degrees of success. The calibration will generally be that rolling a natural 10 will score 1 degree of success, possibly 2 against brutes--high hit points, low defense monsters. Getting an extra +1 degree of success is relatively easy (you'll get a >=15 or a Double 6 or Double 7 23% of the time), but while you could get +2 or even +3 on the roll, that will be extraordinarily rare (you'll roll a Double 8 or Double 9 only 2% of the time, and a Double 10 only 1% of the time). So most monsters will have HP balanced around how many hits they can take with 2 degrees of success from the PCs. At first level, the base damage will depend on the character, but a Warrior with a huge, two handed weapon should do about 10 base damage. So most hits will be 10-20 points of damage, and only if he's very lucky (1% chance) will he do 40 points of damage. I think at first level that 1% chance should probably take the enemy down.

At 20th level, most of the players shouldn't be getting more degrees of success fighting enemies of the equivalent level, but an optimized Warrior with a +3 magic weapon (which applies to both damage and attack bonus) may get one extra degree of success. So on average, the warrior will be doing 2-3 degrees of success. However, I expect that he will be doing considerably more base damage. Assuming magic weapon, a 20th level Warrior with maximum Fortitude and a weapon with a base value of 5, his base damage would be 20. He would also get two attacks most rounds (maybe three, but that's harder to achieve if you need to move between targets). So now he's doing 40-60 per attack, and attacking twice. I haven't taken into account how often he'll miss, but I imagine he'll be hitting most of the time.

Instead of a Warrior, let's consider the Expert. They don't do as much base damage. They do, however, have an ability that increases the degrees of success when they hit with a weapon. They'll probably tend to use weapons that allow them to add Agility to damage, which either have a long reload time (crossbow), or do low damage. So their base damage at level 1 is likely to be 6 at most, and at level 20 is unlikely to exceed 12 (even using a +3 weapon). They do, however, have an ability, Precise Strike, that, if their attack hits (scores at least 1 degree of success), they can increase the degrees of success. This means that at level 1, they should be doing 2-3 levels of success, potentially 12-18 damage. At level 20, they'll probably be doing 6-7 degrees of success on a hit. That's 72-84 damage. But they'll only get one attack per round.

Spellcasters rely on their spells, which should scale in a reasonable way, but I imagine they may apply conditions or spread damage around more often than they'll compete on single-target damage with the warriors.

Hybrid characters will get lesser versions of these features, possibly coming online at later levels and not scaling as quickly (only going as high as +3 damage or +3 degrees of success). They can be combined with each other, or with spells. For example, I intend to give the Holy Knight a 0th-level spell that allows his attacks to do 1 degree higher success against outsiders or undead, 2 degrees at 11th-level (and probably ignore 1 or 2 degrees of resistance as well).

Zones

One thing that I like is using theater of the mind for combat, something that is easier to do in some systems than others. I'd like to make my system friendly toward that, without requiring it. That brings me to the idea of zones, which is the way combat maps are handled in Soulbound. I'll refer to combat using zones as zone combat, and combat using miniatures on a grid as grid combat. 

A zone is an area of combat, defined as much by the terrain as size. A smallish room (up to 30'x30') is a zone, so is the hallway, and also the other small room, while the large audience chamber might be two or three zones. A bridge over a river might have three zones, one side of the river, the bridge itself, and the other side of the river. The river itself could be another zone.

Zones affect range and movement and area of effect, but it's not hard to keep it pretty simple. It takes one action to move from one zone to another. It takes another action to move close enough to engage someone in the same zone as you in combat. Engagement is another word for being close enough to an enemy to attack them with a melee weapon, or for them to attack you. If you're using miniatures, you can just see which miniatures are adjacent, and not need to keep track of engagement specifically.

In zone combat, engagement is an important method to keep track of who you can attack with a melee weapon. Either combatant can initiate engagement, and if multiple enemies engage with you, you can be engaged with multiple enemies. If, however, you are engaged with one enemy and you want to engage with another one, you'll lose engagement with the first enemy. If you are engaged, you take an opportunity attack when moving to another zone or moving to engage with an enemy unless you use a step action to disengage. Engagement is not transitive--if you engage an enemy, and an ally engages them too, and another enemy engages your ally, you aren't engaged in combat with the new enemy. Your ally is engaged with both, but you'll need to engage with the new enemy to attack them, and doing so means you'll no longer be engaged with your current enemy--you'll either need to disengage or take an opportunity attack. 

If you have a weapon with reach you can attack someone in the same zone without engaging. All other melee weapons require you to be engaged. With a ranged weapon with short range, you can attack anyone in the same zone or an adjacent zone, with medium range, you can attack anyone two zones over, and with long range, you can attack anyone on the battlefield assuming you have line of sight.

Usually, area of effect spells affect an entire zone. Some large area of effect spells could affect two adjacent zones or the entire battlefield, though area of effect could come into play.

The air generally counts as its own zone, so someone with flight can easily attack any zone (assuming the zone doesn't have a roof), but he can also be attacked by anyone with a short ranged weapon.

Now I do want rules that also work for miniatures and squares, so I'd want to present both. I don't think you need the engagement rule if you are using miniatures--you engage by moving adjacent to them, and you disengage by taking a step (moving one square with the miniature), if you don't want to take an opportunity attack. The engage action is really just a move action within your zone--you move to get close enough to attack an enemy who's in the same room.

I may also need an action to allow someone to block the way between two zones, assuming the GM agrees the passage is narrow enough. I think in that case, an enemy can't get past him unless they make a roll (probably a Fortitude contest of some kind), but the defender can't take the engage action. Enemies in both zones can engage with him, though. I probably need to make this an action that would work for both zone combat and miniature combat, so I'll need to think of how the rules would apply.

I think I want two levels of difficult terrain, difficult and very difficult (maybe think up a better name later). Difficult terrain halves your movement, and very difficult terrain cuts it to a third. (Remember the Elf feature that ignored a level of difficult terrain? This is where it applies.) Using zones with difficult terrain, I can say that if a zone is difficult terrain, it takes two actions to move, either to engage with someone or to move to a new zone, or three if it is very difficult terrain. Moving from one zone to another takes a number of actions equivalent to the highest difficulty of terrain of the two. If one zone is normal and the other is very difficult, it takes three actions to move to the very difficult terrain or away from it.

Spellcasting

I haven't decided yet whether casting a spell grants an opportunity attack. I'm leaning towards no. However,  I do want to allow an enemy to interrupt a spell. If they ready an action to attack you when you cast a spell, they can force you to make a concentration check to keep the spell. By the same token, if you cast a spell that takes more than one round, then if you are attacked between starting the spell and finishing it, you also need to make a concentration check or lose the spell.

Making a ranged attack may grant an opportunity attack, however, including a ranged spell attack. Perhaps both would require a concentration check to still attack, otherwise you lose the spell or the ammunition as the magic or arrow goes wide.

Finally, I'd like to borrow from Pathfinder 2e's way of sustaining spells. You don't cast one spell and concentrate on it. Instead, you need to use one of your actions to sustain a spell. You can sustain more than one spell, but you quickly run out of actions that way. Pathfinder 2e doesn't let you end concentration on a spell by just doing damage to the caster--there are no concentration checks for that. Instead, you stop someone's sustained spells by causing a condition that prevents them from using an action to sustain the spell. I do like having to concentrate to maintain a sustained spell when you're hurt, so I may keep that aspect of concentration. Your degrees of failure determine how many sustained spells you lose if you're sustaining more than one spell. I may let the player decide which ones they lose.

Two-Weapon Fighting

Here's another place I borrow from Soulbound. You can attack with two weapons with one action, either attacking the same enemy or two different ones you're engaged with. However, in order to do so, both weapons need to have Agility for both attack and damage (currently, there are only two: daggers and rapiers, but I could see adding unarmed attacks for martial artists, perhaps some paired weapons purely for dual wielding, maybe even bucklers will be treated as an offhand weapon). However, for both attack and damage, you divide your Agility in two and apply half to each, rounding up for your main hand (whichever is holding the larger weapon), and rounding down for your off hand. This is similar to what you do in Soulbound, where you divide the number of dice into dice for one weapon and dice for another. I may add talents for Two Weapon fighting. If you have an Agility of 4 or more, you can take a Talent that will let you add +1 to each weapon's attack and damage, and if you have an Agility of 6 or more, a Talent with the first one as the prerequisite will let you add +2 to each weapon's attack and damage. I may also add +1 to Defense when you are wielding two weapons but only attack with one, but I haven't decided whether that's automatic, or part of these or a different Talent.

Resistances

Another thing I'm mulling over is resistances. Some creatures are just hard to hurt with certain elements. For example, casting a fire spell at a fire elemental should do a lot less damage than against a plant creature. However, I don't like the idea of complete immunity. There should be at least some way to harm enemies with fire spells, even if they're resistant.

My initial idea is to have resistance that builds off the idea of degrees. When you hit a fire resistant monster with fire and achieve any degrees of success, the number of degrees of success is reduced by one. More resistant enemies can have more degrees of resistance. A fire-breathing dragon has two, a fire elemental has three. However, when you have an enemy with three degrees of resistance, that can turn a degree of success into two degrees of failure. If I have fumble rules (something that I'm still considering), then I'm not sure that's fair. However, if I start setting limits: a resistant creature can't reduce the success of the roll below a near miss, for example, then I run into an order of operations problem. 

Let's say I introduce a talent that says when you score a success against an enemy with fire, you deal an extra degree of success, or two degrees of success if they're resistant.

Let's get back to my fire elemental with three degrees of resistance. I score two degrees of success, they apply their resistance to turn that into a near miss, and then I apply my talent--only I can't, because the talent says I can't apply it unless I have a success first. Okay, let's say I solve that issue, and I say that I can apply the resistance first, then the talent--then it goes to two degrees of success again. But if I go the other way, and add my two degrees of success first, bringing it to four, then deducting three degrees of success, I only have one degree of success. By applying the resistance first, I actually did more damage than I would have if I applied the talent first, because I ran into the limit.

I think the easiest way to do this is to not set limits to resistance, and allow it to turn a hit into degrees of failure. It's really no different than attacking someone with a very high defense. Failing to do damage is more a matter of the heavy armor than a fumbled roll. You can just open yourself up if your attacks, no matter how skillful, are ineffective.

This does still leave the problem that I still have some degree effects with conditions. I don't want to change the Precise Strike rules, where I get more degrees of success when I hit, since I don't want to make my roguish characters more likely to hit than anyone else. I think, instead, I'll apply the conditional degree effects only if the condition still holds after the other degree effects. It seems like I can, however, make resistance unconditional, and adjust the elemental damage to something like "Your fire attacks ignore two degrees of fire resistance. In addition, any successful fire attack gains one degree of success."

Recovery

I said this earlier, but I want PCs to recover hit points after every battle. I haven't decided yet whether I want this to be a short rest thing, in that they need to rest for an hour after a battle and recover all their hit points. If so, I may also tie it to recovery of spell points. Alternatively, I may just make it so that if you have five minutes to catch your breath after a battle, you recover all your hit points. (In this case, I'd keep the spell recharge rate by hour and not require rest to do so.) The key to understanding this is that hit points are not health. They measure your endurance, your ability to roll with the punches, and otherwise avoid serious injury. Only when your hit points go down to 0 are you hurt enough to take you out of the fight. And any significant injury is sufficient to take most people out of a fight.

When you recover from being taken down to 0, you return with an penalty. Some games call these Wounds. They can be tied to levels of exhaustion in D&D (especially the One D&D version which has ten levels instead of five). In earlier posts, I called it Fatigue. But I think I'll borrow from other games and call this Stress. Stress can be physical--injury, bruises, sore muscles--or mental--being worn out, discouraged, depressed. The total amount of Stress you can endure is Fortitude (minimum 1) + Will (minimum 1), for a minimum of 2. Most players will want more than this. For each level of stress, you get a -1 to all rolls. Once you exceed your maximum, you are broken. This doesn't necessarily mean you are dead, but it does mean your character is no longer an active participant in the adventure, and cannot make any rolls. You recover one point of Stress per full night of rest, or two points if you rest in a comfortable and safe location (in town, or your team base, or some other safe area).

Going down to 0 is one way you can gain Stress, but not the only way. Traveling in hostile terrain (arctic or desert conditions, for example), 2 degrees of failure on some checks, the price to turn an important Near Miss into a success.

So, if you regain hit points each time you finish combat, that means you need less HP, right? Well, not so fast. In most groups, players are going to be close to full health before most battles. Also, damage can stack up quick if the enemy rolls a dreaded Double 10. So you don't want to make the HP too much lower. Here's what I'm thinking--you start with 10 + Will (minimum 1) + Fortitude (minimum 1), and add a fixed amount per level in each class. This amount can range from 2 through 5, depending on the class. Initially I'm thinking 5 for Warriors, 4 for Skirmishers and Champions, 3 for Experts and Adepts, and 2 for Magi. The HP will start higher, but scale slower. Pretty much everyone will have a decent Fortitude or Will, though both may be rare.

Death

So if you don't die when you go down to 0 hit points, and you don't die from hitting your maximum Stress, can you die in this game? Well, two facts come to mind: One, death usually sucks. Two, fear of death is a great motivating factor.

In general, going down to 0 does not mean you die. But an enemy can use three actions to coup de grace a downed character. If the entire party goes down, then it's understood that the surviving enemies could very well kill them. Not being able to fight back as they put you out of your misery will definitely kill a character. A coup de grace will definitely be part of the rules. It will take three actions, so most enemies won't do it while in the middle of combat, but a GM can use it to put some fear into his players.

The GM can also declare that some actions are so risky that failure may mean death, such as trying to  jump over a gorge. He should inform the players before they attempt to do so, though.

Another way to die is to go down in a Blaze of Glory.  This is a rule I'm borrowing from Soulbound. If you're at or are knocked down to 0 hp, you can declare that you're going down in a Blaze of Glory. You immediately stand up with 1 hp and you take your turn, your spell points are fully recharged, you have three actions, you are immune to all damage and all conditions, all rolls you make are Double 10s and ignore resistance, and all rolls to save against your rampage subtract two degrees of success. At the end of your turn, you immediately die and cannot be brought back (I'm not sure whether there will be resurrection in the game at all). Then play returns to where it left off in the turn order before you took your turn.

Can this be abused? Definitely. It's up to the GM to make sure it's not. For example, the first time it happens, let the player make a new character at the same level. If he does it again, the next character can be a level lower, and then another level lower. Even going out in a Blaze of Glory doesn't make a 1st level PC stand out among a group of 7th level PCs.

Conclusion

At this point, I think I'm done with this series of posts. I've described the system and how it works, thought through some numbers, and done about as much as I can do without playtesting. In some ways, coming up with the basic rules are easy. The hard part is in the details: working out the features and progression of each class, coming up with all the spells and spell schools, creating monsters, writing it all out in a book, and playtesting it all while tweaking the numbers. Overall, it's a lot of work, and I'm not likely to do it unless I have a group that's interested in playing this game. We'll see.

Wednesday, February 01, 2023

2d10 Equipment

I could spend a lot of time on equipment, but I intend to keep this simple. Besides, the only equipment most people are interested in is weapons and armor, so I'll focus on that. 

Each weapon has an ability score used for attack, an ability score used for damage, and a constant added to damage. This constant is between 0 and 5, most commonly 3 for most one-handed martial weapons. Most weapons use Agility for attack rolls, and Fortitude for damage rolls, but there are exceptions.

The first exceptions are the crossbows, daggers, and rapiers, which all use Agility for both attack and damage. Each of them has a disadvantage. Daggers have a 0 damage bonus. Rapiers are slightly better at 2 but are special weapons requiring particular training.  And crossbows take significant time to load.

The other exception are heavy, two-handed weapons. These use Fortitude for both attack and damage. There are a few special one handed weapons, such as Dwarven waraxes, that have this feature as well. Normal swords need Agility for attack and Fortitude for damage.

Armor will work closer to a cross between 5e and 3.5e. They'll be divided between light, medium, and heavy, though unlike 5e, you don't need training in light to get training in medium, though you will need training in light or medium to get training in heavy. Like 5e, the armor class will be calculated using a base value plus Dex (or in this case, the higher of Agility or Mind). However, the maximum Agility or Mind bonus allowed will depend on the specific armor, rather than just being dependent on the light, medium, or heavy type. I'll probably also bring back an armor penalty based on the specific armor, though it will not grow to the ridiculous heights it could in 3.5e and Pathfinder.

One thing I want to do more with is Crafting. I want rules to craft not just ordinary armor, but magical armor. This will take two forms: casting enchantments on ordinary armor, or crafting (or improving) armor with rare materials. Those materials can be quest rewards or discovered while adventuring, but they usually can't be purchased. Whether using raw materials or casting spells, there will also be an estimated cost in gold, which will probably be about a quarter of the purchase price of the item (most items cannot be purchased, but there is an attached price for reference). That amount represents costly materials and components needed to craft the item.

Crafting an item is a long-term task. To complete an item will require a number of success tokens proportional to the difficulty of creating the item. Each day, the player spends an amount equal to the total cost divided by the number of necessary success tokens, and rolls a Crafting skill check. Each degree of success adds a success token, while each degree of failure subtracts a success token. The item is complete once the number of success tokens equals or exceeds the number needed to complete the item. Notice that very good rolls could result in the project costing less than the estimated cost.

Casting a spell on the item is a ritual, that usually takes multiple hours since the spell point cost of making an enchantment permanent is greater than a magus's total spell points. Remaining focused on the spell during the course of the ritual generally requires multiple rolls.

Crafting tends to take days, rather than hours, but it has the potential to cost less, and a failure on one roll doesn't necessarily ruin the project. Moreover, projects may be put aside and returned to later. Casting a spell takes hours, but one failed roll means the whole spell is lost, along with any material components.

Tuesday, January 31, 2023

The ABCs of Character Origins

Gruff underground dwarves, woodland elves, pastoral hobbits--we all know the stereotypes. Recent versions of roleplaying games have tried to lean into them a little less fully. Allowing them, sure, but also allowing characters to play against type, and build the characters they want.

To that end, the newest version of D&D tied all the ability bonuses to backgrounds, which generally reflect the career you had before adventuring, while making the racial options (now called species) more focused on biological traits rather than cultural ones. For example, by giving dwarves tremorsense, but no longer the usual weapon training. While I appreciate making things more open, I feel like this goes a little too far.  For one, neither background nor species reflect the culture of the character, and I'd like that to have a role.

So rather than just selecting species and background, I think you should build your characters with ancestry, background, and culture.

Ancestry

Ancestry is the term used by Pathfinder 2e, but I think I prefer the word Kind, partly because it fits well--dwarvenkind, elvenkind, and humankind. I don't like species, because it overlooks a key aspect in many fantasy realms: they can interbreed.

I like giving each Kind an ability bonus (with options), a couple of traits, and a decent list of talents (feats) which are specific to them. Here's my first draft for the four main ones: humans, dwarves, elves, and halflings.

Dwarf

Ability: +1 to Fortitude or Will
Traits: Low-light vision and blindsight (10'), Dwarven Toughness (increase levels of fatigue and ignore the penalty for the first two or three levels)

Dwarven Talents: Resistance to Poison, Hard to Knockdown

Elf

Ability: +1 to Agility or Mind
Traits: Low-light vision, Ignore 1 level of difficult terrain

Elven Talents: Ranged attacks bonus, Elven magic

Human

Ability: +1 to any
Traits: Extra talent and skill and specialization

Human Talents: Quick learner (additional skills + languages), Dabbler (learn a magic school even if you don't meet pre-requisites)

Halfling

Ability: +1 to Agility or Will
Traits: Small, Lucky (roll a Fortune die when roll low double)

Halfling Talents: Hard to See, Courageous


I want to get rid of darkvision as it exists in D&D 5e. For one, everyone has it, and two, the way it works based on range from a character doesn't make much sense. Instead, I'd give low light vision, where dim light is treated as bright light, and treat light according to the distance from the source, not from the one seeing it. For complete levels of darkness, I would give dwarves not darkvision, but blindsight. That can have a limited range, as it's specifically understood to not be sight, but to act like sight. Since no one has a way to see through complete darkness, we don't have to worry about magical darkness working against darkvision.

One of things I'd like to do is take some of the features which are iconic traits in other games and make them talents, which are like feats in that you can take them at certain levels. But I won't make players choose between talents and raising their ability scores.

For people who are of mixed-kinds (half-elves, et cetera), I'll let them choose the ability of one kind and one trait from the other (possibly two, if each Kind has at least three traits). But they would have access to all of the talents of both Kinds, as well as a special talent that lets them pick a trait from either parent Kind.

Culture

Culture is how someone is raised. It can be connected to their kind, but it doesn't have to be. I'd expect to have cultures such as Dwarf Hold, Elven Forest, Human Town, and Halfling Settlement. But I'd also have other ones, such as City (with the understanding that cities are mostly cosmopolitan, and many Kind settle there), Rural, Wilderness, Seafaring, and Plains. The culture would grant a language, weapon training (often in martial or specialized weapons), perhaps armor training, and +1 to an ability depending on the culture (usually granting a choice between two possible abilities). There would also be a skill and a specialization based on the culture.

Background

Background is an important part of a character's past. It basically represents their career prior to adventuring. They may have been a smith or a miner or a guard or a wizard's apprentice or an acolyte. The background grants +1 to one of two abilities, a skill and specialization related to their background (Labor, Craft, and Profession for a lot of them, but perhaps some of them offer more adventuring skills), and some basic equipment associated with the profession.

Summary

When building a character, players select a Kind, a Background, and a Culture. This grants them three ability points, which they can put all in different abilities, the same ability, or spread out, as long as no ability exceeds 4 at least one. Their Culture and their Background should each grant them a skill and a specialization, their culture grants them a language and weapon training, and their Background grants them some basic equipment. This is before selecting a class.

Expert and Expert hybrid classes (Adept and Skirmisher) get the most skills and specializations. But I think that even Warriors, Magi, and Champions get some skills and specializations.

Monday, January 30, 2023

2d10 Classes

Classes are an important part of Dungeons and Dragons. There are four basic classes, which have been around a while: cleric, magic-user, thief, and fighting man. Nowadays, we call them cleric, wizard, rogue, and fighter. But part of what makes recent editions of D&D fun are the wide variety of classes (12 from the PHB + 1 from Tasha's), and the subclasses, of which there are over 100 official ones, and thousands homebrewed ones.

Classes and subclasses are the main way that players try to capture the archetype they want to play. Building the character you want involves selecting the right base classes and subclasses, and often times multiclassing to get two or more classes, and sometimes additional subclasses.

There are a number of games that try to do away with classes altogether. GURPS and Mutants and Masterminds, for example, rely on point systems that allow you to build, in theory, any character you want. The problem is that point systems tend to be really complicated, and building a character that way can take an excruciatingly long time. There's software to help, and you'll probably need it.

I think for my 2d10 non-OGL game, I want to keep the idea of classes and subclasses, but simplify things a little. Many games boil down the game to three classes: Warriors, who do the fighting, Experts, who have a lot of capability with various skills, and Mages, who cast magic. That is, in fact, what D&D does for sidekicks--NPC party members who have a stripped down character classes. In this approach, Warriors stand in for Fighters, Experts replace Rogues, and Mages replace both Clerics and Wizards, depending on which spells they have. But this isn't the only game that does three basic classes. There's also Fantasy AGE, True20, Worlds Without Number (which also adds Adventurer, which functions as a hybrid of any two of the three main classes), and Cypher, which all divide classes this way, though often with different names.

I think I want to start with the simplified three classes, but also introduce three hybrid classes, and then add 5e's concept of subclasses. In this system, each class in D&D can be represented by a subclass in the 2d10 system.

Three of the classes are the same as used elsewhere: the Warrior, the Expert, and the Magus*. But the other three are hybrid classes: there's a Warrior-Expert hybrid (let's call that a Skirmisher), a Warrior-Magus hybrid (Champion), and an Expert-Magus hybrid (Adept). Each of these helps to fulfill an archetype, and the subclasses make those more explicit. For example, Clerics and Wizards fit under the Magus class, Paladins and Rangers subclasses can fit under Champion (or possibly Adept for Ranger), Bards are an Adept subclass, and Monks are a Skirmisher subclass.

One thing I want to do is allow the hybrid spellcasters not to feel underpowered compared to the Magus, while making the Magus the best spellcaster. To that end, I think that the Champion and Adept will get access to fewer spell schools, but some of them will be unique to their classes (or subclasses), fewer spell points, and have their spell points recharge more slowly. But they'll still be able to cast spells up to the 20th level, and if they invest in Will, will still have more than enough spell points to make it work. The spell point recharging will be part of the class table, so to determine the total amount, you can just add them together. Champion and Adept will recharge their spell points at a rate of one-quarter their level per hour, rounded to the nearest whole number. So at level 1 they won't recharge at all unless resting. Magus will recharge his spell points at one-half his level, rounded up. Finally, the Magus will have a feature that will allow him to meditate to recharge all the spell points he would receive in the next hour in five minutes, but at a cost. Possibly a point of fatigue, but I'm actually thinking that reducing his max spell points by the same amount until he rests might work better.

So here's a rough sketch of classes and subclasses:

  • Warrior - This class will get a scaling bonus to damage. It is also one of the simpler classes, needing only Fortitude and Agility.
    • Berserker - Like the Barbarian.
    • Archer - Basic, non-magic archery
    • Soldier - The basic fighter.
  • Expert - Aside from getting more skill training and specialization, they also get a precision strike (like sneak attack), that increases the degree of success on attacks in certain situations, but only on a hit. Since damage is a base amount times degrees of success, this can be a significant bonus to damage.
    • Thief - I'm considering giving them a feature that lets them "steal" from the party. Basically, if they're in a situation when it would be handy to have something another player has (like a potion or scroll), then can search their pockets, and other players can offer up items. 
    • Alchemist - I haven't fully decided how this works, but a non-magical maker of dangerous items could be fun.
    • Investigator - I want an Expert that's less Thief and more Investigator, able to find secrets and put together clues. 
  • Magus - The primary spellcasters get more spell points, more spell schools, and they recharge spell points quicker. They can also ritually cast spells, which allow them to spend more spell points than they actually have.
    • Wizard - They have spell schools that emphasize not just damage but also the manipulation of magic.
    • Priest - The priest has spell schools that heal and buff.
    • Druid - The nature priest. I think I'd like to add shapeshifting, but I'm not 100% sure that I want to make that specific to the druid. They have unique nature spell schools, plus a mix of healing and damage, but not the buffing or magic manipulation.
  • Skirmisher (Warrior-Expert) - As a cross between Warrior and Expert they get some of both. The scaling to both damage and precision strike is slower, and they get fewer skills and specializations than Experts but more than Warriors.
    • Scout - Their job is to sneak in and observe. Is a ranged attack specialist, with high stealth.
    • Swashbuckler - Like the rogue subclass, they get proficiency in rapiers and bucklers, and are particularly good at Acrobatics (Stunts)
    • Martial Artist - The basic monk, but with less emphasis on the mystic, more emphasis on cool moves and traversal.
  • Champion (Warrior-Magus) - This is a cross between Warrior and Magus. One of their key features will be Empowered Strike, which allows them to use Will instead of Fortitude for damage with weapons. While they get fewer spell schools and spell points than Magus and their spell points recharge slower, they will also get some unique spell schools based on their subclass.
    • Arcane Archer - Their spell schools empower their arrows.
    • Holy Knight - The paladin. Their spell school(s) is particularly effective against undead and outsiders, though not useless otherwise.
    • Witch Knight - The gish.
  • Adept (Expert-Magus) - This is a cross between Expert and Magus. They will get Precision Strike but it scales more slowly than Expert, more skills and specializations than normal (maybe even as many experts, but I haven't decided yet), and spellcasting, which will be about equivalent to the Magus
    • Bard - Like the D&D class. They get at least one unique spell school of magical songs.
    • Shadow - Basically like the Way of Shadow Monk, Shadowdancer, Ninja, or Assassin. Their unique spell school(s) emphasizes shadows and stealth. 
    • Ranger - Like the D&D class, their emphasis is on nature, with access to spell schools that support that. They will be primarily ranged attackers.

In order for this to work, the subclasses will need to kick in at 1st level, so that features that define the subclass (like unarmed fighting for the Martial Artist) can be added at first level. Otherwise it'll be similar to subclasses in D&D 5e, with features that come in at regular intervals. Maybe not the same intervals as 5e: perhaps first, third, seventh, tenth, fourteenth, and seventeenth.

As well as these hybrid classes, I also intend to allow multiclassing. One of the fun things about D&D 5e is the ability to multiclass and get interesting features. The trick, though, is to make sure there's a price for doing that that's significant enough that people wouldn't be tempted unless they have a specific idea.

* I chose the term Magus partly because I like the word, and partly because it gets to the origins of the term magic. The Magi (it's the same term used in the Bible for the visitors of Jesus, but not necessarily the same people) were originally a priestly caste/clan in ancient Babylon and Persia. Their rituals were exoticized by the Greeks and became the origin of the idea of magic. It also speaks to the fact that in the ancient world, there wasn't really a distinction between magic and religion. Rituals that appealed to the gods and/or spirits to do what you wanted was religion when you did it and magic when foreigners did it.

Friday, January 27, 2023

2d10 Magic System

 In this post, I'm exploring magic systems in RPG, and what I want to borrow for my 2d10 system.

Dungeons and Dragons 5e uses a variant on its Vancian magic system. In older editions, magic-users would have a number of spell slots at different levels (the spell levels you had access to weren't the same as your class or character levels). Magic-users would fill those slots with the spells they wanted to cast that day (this was called memorizing the spell). Then once they cast their spell, they couldn't do it again as that slot was now empty. The only way to cast a spell twice was to put the same spell in two slots (memorizing it twice).

Fifth edition still uses the term slots, but it works differently. The term slot is now outdated, though it's still the term used. The spells you have prepared don't match the slots, you don't lose the spell once you cast it. Instead you spend a spell slot to cast a spell, and can choose which spell you're spending the spell on only when you cast it. If you want, you can use all your slots to cast a spell again and again, assuming that the level of the spell is equal to or less than the level of the slot.

But D&D does have an alternative magic system, explained in the Dungeon Master's Guide, called spell points. When you want to cast a spell, each spell has a cost based on the spell level, and the number of spell points you have depends on your spell slots.

What I'm proposing is something similar to that, but based instead on the spellcasting in MERP, Rolemaster, and Against the Darkmaster (VsD). In those games, instead of learning individual spells, you learn a set of spells (called a Spell Lore in VsD). As you increase in levels, you can cast the higher level spells in the Spell Lore. So all fire spells are in the Eldritch Fire Spell Lore, and as you level up you gain spells  from a fire touch attack to a bolt of flame to a ball of fire. The cost of the spell in Magic Points is equal to the spell's level, which is equal to your character level.  The number of Magic Points you have depends on the class and your magic ability score and is multiplied by your level. 

However, I think that I want to let the Magic Points recharge more quickly than VSD does. So that the caster can regain a portion of their spell points every hour (similar to the Aetaltis campaign world). In that case, we'll need to keep the scaling on spell points slower, and make spells more expensive.

VsD has ten levels, and a spell for every level. D&D grants new spells every other level, but calls the spells wizards gets at level 1 first level spells, the ones they get at level 3 second level spells, and the ones they get at level 5 third level spells. This is definitely confusing. I think I'd like to clear that up with my system.

So let's call the spell lists Spell Schools (as that's how D&D groups them). Every spellcaster gets a number of Spell Schools (exact number to be decided when we get to classes). There are, for example, the Fire School, the Water School, Enchantment School, Song School (for the bards, of course). Each of the schools have spells at different levels, but not necessarily every level. In fact, I'd like the distance between the spells to increase as levels go up.  My initial thought is 0, 1, 2, 4, 6, 9, 12, 16, 20. That's nine levels of spells, and you don't get the highest level until level 20. The number of spell points each spell costs should be equal to the level. So a level 0 spell costs nothing, and you can cast it as many times as you want. Level 1 spells cost 1 spell point, level 5 spells cost 5 spell points, and level 20 spells cost 20 spell points. One thing I like is that you don't need to have spells at the same levels for every School. You can, instead, have spells at different levels, and more spells in certain schools.

That indicates that high level spellcasters should have at least 20 spell points if I want them to be able to cast any 20th level spells. With that in mind, I can figure out how to calculate spell points. My plan is to make it Will plus a class constant (which ranges from 0 to 5), times the base modifier. The base modifier is the same scaling as skills, which is equal to the character level divided by four rounded up. So 1 for levels 1-4, 2 for levels 5-8, 3 for levels 9-12, 4 for levels 13-16, and 5 for levels 17-20.

The maximum any ability can be at level 1 is 4, and let's say mages get 5 spell points, so at level 1 they have 9 spell points. However, that doesn't increase until level 4, where, if they put 1 point in Will, they now have 10 spell points. At level 5, however, the base modifier increases by 1, and they have 20 spell points, just in time to cast level 5 spells for 5 spell points, meaning they can cast 4 before they run out.

The maximum number of spell points they can reach is 60. Which is a lot of first level spells, but only three level 20 spells.

But as I discussed earlier, I would like them to recharge spell points every hour. I'm not sure how fast that should happen. I could see making it as slow as the base modifier, or making it Will + class constant, or even making it the caster level (that might work best with multiclassing, if some classes add 0 or half to the recharge number). Right now I'm thinking half the level for pure casters, and a quarter the level for quarter casters.

D&D has a concept called upcasting, and VsD has a similar concept called spell warping, where you can increase the effect of the spell if you cast it at a higher level. There was a more flexible version of this called metamagic in D&D 3.5 and Pathfinder. I'd like to borrow this, but rather than a higher level, I'd like to add a multiplier on the spell point cost. This means that you don't need to be higher level to make a spell more powerful, but you can burn through your spell points quickly if you enhance the spell too much.

But you can also cast spells that are upcast to use more spell points than you have. This will be the basis of ritual casting. You can either share the burden with another caster who knows the spell, or you can cast slowly enough that you recharge the spell points as you cast. That takes hours, maybe a whole day, and you may have to roll Concentration to see if you can maintain the casting that long.

Finally, there's a question of which ability to use for the casting stat--whether it's a roll to cast, or a DC the target needs to save against. Usually this is the base modifier plus an ability score. It should probably be either Mind or Will. After some consideration, I think that spells which have a physical effect should use Mind, and those that have a mental effect should use Will. This likely means different stats depending on the spell school. It could also be that attack rolls should use Mind while saving throws use Will. I believe that saving throws will be 10+Will+base modifier.

Tuesday, January 24, 2023

Revisiting 2d10, doubles, extra dice, and degrees of success

In my first post on this topic, I talked about 2d10 as a variant for Dungeons and Dragons, and focused on the ways it interacted with its existing systems. Because of that, I limited how far I used things such as degrees of success. Now that I'm considering, because of the OGL mess, how I would build a system around 2d10, I'm rethinking how I did things in that post, and the subsequent Weal and Woe pools.


Math First

First, let's take a step back and consider how much effect do you get from rolling an extra die (3d10), and then selecting the best or worst two. Let's revisit this table from my Abilities and Skills post:

Odds of rolling different targets with 2d10 at different levels of ability.

As you can see, even with no training a character would usually pass a test with a target number of 10, a character with either a maximum ability modifier or skill training and specialization (which will give a similar result as those with decent Skill Training and a decent ability score) have a good chance of succeeding on a Medium test, and those with all three have a good chance of meeting a target number of 20 at low levels (but those with only one or two of Skill Training, Specialization, or maximum ability modifier become more likely to reach it at higher levels).

Target numbers of 25 or above are basically there to give those who have mastered a skill something more challenging at higher levels. A target of 30 is almost impossible--it should only be attempted at high levels, and adventures shouldn't hinge on successfully making that check. In some ways, 25 and 30 are more useful to show the odds of the most capable character getting one or two extra successes versus DC 20.

So that's what it looks like if you're only rolling two dice. What if you're rolling three and taking the two best. Then, your odds of success look something like this:

Odds of rolling different targets with 3d10 keeping the two best at different levels of ability.


This makes the higher targets of 25 or 30 look more achievable, as low odds basically double (high odds only change incrementally).

What if you're stuck with the two worst?  That looks something like this:

Odds of rolling different targets with 3d10 keeping the two worst at different levels of ability.

Now really high rolls look practically impossible. Most of the odds that were less than 50% before are effectively cut in half. This suggests that target numbers of 25 and even 30 at high levels are something you should only throw at your players when they attempt something ill-considered and you expect them to fail--but you want to give them a chance to do something epic if they succeed.

Weal and Woe, Mostly Woe

So we want the probability shifting that comes from throwing an extra die, but we probably want to call it something different from Weal and Woe, which is what I was using earlier. I suggest that when a player rolls an extra die, you call it a Fortune die, and when the GM rolls the extra die, you call it a Doom die. This applies no matter what circumstance grants it (spells, favorable or unfavorable circumstances, aid from another party member). The reason for this is that I want to keep my Weal and Woe Fortune and Doom Pools as an optional element, and if we have a mechanic called Fortune dice, we can easily add the idea of a Fortune Pool, as the resource from which those Fortune dice come.

We can also give each player character a fortune point, similar to D&D's inspiration. They can gain a Fortune Point whenever they roll doubles, and spend them to roll a Fortune die. Note that unlike the Advantage/Disadvantage, spending a die for Fortune has no effect on whether the DM rolls a Doom die. You merely have to declare you're doing so before the DM discards a die, and then you each roll, and remove a die in the order you roll.

Degrees and Doubles

In my first post introducing the 2d10 mechanic to D&D, I included two mechanics that interacted with one another, doubles and degrees of success. I stipulated that degrees of success only applied to ability checks, while doubles applied to all rolls that would use a d20 in D&D (including attacks and saves), and had to explain how to handle doubles in each situation.

That said, if I'm creating my own system more or less from scratch, I don't have to adapt it to how D&D handles different types of d20 rolls. That allows me to smooth things out more and make it more consistent. So let's adjust things this way: all rolls have degrees of success and failure. This includes attack rolls, saving throws, and ability checks (though since they're all the same, we no longer need to divide them up this way).

So an attack roll can have one, two, three, or more degrees of success, while a saving throw can have one, two, or three degrees of failure.

That also lets us approach high doubles and low doubles differently. A high double increases your degree of success by one, while a low double decreases your degree of success by one. However, universally, degrees of success and failure are every 5 points above or below the target number. Therefore, it may be easier to treat a high double as adding five to your roll, and a low double of subtracting five from your roll. This results in moving you up and down the success ladder the same, and may be easier to remember. (And it's definitely useful for doing opposed rolls, where a double could change who wins.)

We can also use the skill descriptions to describe what various degrees of success mean for different skills, and spell descriptions for what degrees of failure mean for saving throws (it might be useful to take a look at Mutants & Masterminds, which does this already for a lot of its abilities, with certain conditions being stronger versions of other conditions, so that when you fail against an attack that applies a condition, the degree of failure determines which condition applies).

One thing to think about more in-depth is the concept of zero degrees of success, or a Near Miss. In many contexts, this is simply a failure with no additional consequences. You failed to pick the lock, you missed the enemy, etc. But I'd like to encourage GM's to allow it to be a success with consequences, or at a price. This is especially the case for high, almost impossible to achieve target numbers (anything higher than 20 for most parties). If it's very hard for your PCs to reach the target number, there's still a decent chance of almost making it. In that case, it may be worthwhile to let them have it, but at a price.

So here are some ways GMs can use a Near Miss:
  • A failure with no additional consequence. You don't convince the king, but you don't offend him either. You don't find the evidence you were looking for, but you can keep looking. You miss the enemy, but assuming he doesn't kill you in the meantime, you can try again next round.
  • A partial success. You try to grab the gold, but only get a few coins. You try to catch the falling potions, but only rescue one. In these cases you did part of what you were trying to do, but not all.
  • A success, but it takes ten times as long. This is particularly useful in a situation where the character can simply try again. It's less interesting to have the player roll multiple attempts than it is for the GM to just declare that they succeed, but it takes a while. Especially when the GM uses this to increase tension. What would have taken a round on a success instead takes a minute. What would have taken a minute takes ten minutes. What would have taken an hour takes all day. GMs should always present it as a choice: "After a minute of poking at the lock, it's clear this is going to take a while. Are you going to keep at it, knowing that a patrol may come by at any minute?" Then the GM uses a random roll to determine whether the patrol arrives, using their favorite method to determine if a random encounter happens.
  • A success with a consequence. You succeed, but something bad happens as well. You get the lock open, but made enough noise to attract a guard in the meantime. You convinced the king that there's a problem, but his solution is not one you like. You avoid the pit trap, but now your party is separated by it with no way to reconnect. In general, you don't want the consequence to be worse than what would have happened with a degree of failure. GMs don't usually need to give the players a choice to use this option.
  • A success at a price. You succeed, if you're willing to pay the price. That price may be gold to pay the guard, or a level of Stress, or a valuable item falling from your pack to the jagged rocks below the cliff you're climbing. In this case, the GM should present this as a choice.

Stress

Many games have different pools for different types of injury. Consider for example the Warhammer Age of Sigmar RPG Soulbound. This has Toughness (an HP pool which you recover after every battle), and Wounds (more significant injuries that take time to recover from). D&D doesn't exactly do this, but the exhaustion mechanic (and especially the one introduced in One D&D) gives us an ability to give players conditions that affect their performance and that take time to recover from. Many tables use the exhaustion mechanic to introduce penalties when players lose all their HP and go down and need to be healed to get back on their feet. With the 5e version, that is very punishing.

But I do think I want something along these lines. Let's call it Stress for now. You receive a level of Stress whenever you go down to 0 HP in combat. It can also be the price you pay to turn a Near Miss to a success, or if you fail an important roll (say you're traveling in a hostile environment and fail your Survival check), or it could represent an injury you receive from a trap. For each level of Stress, you subtract 1 from all your rolls, and when you exceed the maximum, you're down for good. This can mean dead, or just collapsed, unable to get up again.

In One D&D the maximum number of exhaustion levels one can reach is equal to 10; after that you die. I think I'd make that something dependent on the character stats. For example, you can make the maximum equal to the character's Fortitude + Will ability modifiers, but you would need a minimum value for players who decide to dump both Fortitude and Will. I would say if you have 0 in an ability score, you can use 1 instead. (So if you have Fortitude of 3 and Will of 0, you'd have 4 Stress Levels.)

Recharging

D&D 4th edition had at-will, encounter, and daily abilities, and encounter abilities would recharge after each battle. As a whole, people didn't like it. But recently, I've played a number of video games with a similar mechanic, such as Chained Echoes and Pillars of Eternity 2. I like how you can go from battle to battle, and only worry about retreating when you gain wounds which you don't recover from quickly. From tabletop games, I'm inspired by the Soulbound Toughness and Wound mechanics mentioned above, and by the spell point mechanic used in Aetaltis, a D&D 5e campaign. In Aetaltis, spell points recharge, and you regain a number of them every hour.

A Stress, wounds, or whatever I decide to call it gives me a more durable mechanic for injury, that comes with a built-in penalty to rolls. So on top of that, I can have a hit point pool that recharges rapidly after a battle. For spell points, I can have those recharge at a rate dependent on Will and class every hour. This will require a smaller maximum number of spell points compared to spell slots. In general, it'll probably be more spells at low levels, and fewer at high levels, with spell points allowing a few high level spells to be cast or a number of low level spells.

I'll talk about my ideas for magic in a later post.

Thursday, January 19, 2023

Abilities and Skills

Here, I'm considering how best to design a non-OGL role-playing game. See my other 2d10 posts.

Abilities

Dungeons and Dragons famously has six ability scores: Strength, Dexterity, Constitution, Intelligence, Wisdom, and Charisma. Each ability has a value of between 3 and 18 for humans (originally the result of rolling three six sided dice), and gives a modifier of one for every two points above 10, and a modifier of negative one for every two points below 10.

While this is traditional, it's also old fashioned. If I were to redesign it, I would make the following changes: there is no difference between the ability score and the modifier. Instead, your score is your modifier, and your ability scores go from 0 to 5 (alternatively going below 0 for non-humanoid monsters).

But let's simplify it from six abilities to four. We need a good mix of physical and mental, and of abilities that represent strength and dexterity. So we have an ability for physical strength: Fortitude. And an ability for physical dexterity: Agility. But we also need an ability for mental dexterity: Mind. And finally one for mental strength: Will.

So we have our four abilities. Fortitude is a mixture of Strength and Constitution from D&D. It represents physical toughness and endurance, as well as physical fitness and muscle strength. Agility is most like Dexterity from D&D. It represents flexibility, accuracy, and muscle memory. Meanwhile, Mind is a good match for D&D's intelligence, and maybe the part of Wisdom that relates to noticing things and paying attention. It represents mental adaptability, quickness of thought, reasoning, and recollection. Finally, Will matches for both Charisma and the part of Wisdom that represents willpower. It's force of personality and stubbornness.

When creating your character, players start with 6 points to distribute among their four abilities, and can't put more than 3 in any one. So you could do 3-3-0-0, 3-2-1-0, or 3-1-1-1, and still put a three in your primary stat.

The problem with D&D is that the abilities are not created equal. Almost everyone needs Dexterity (for their armor class), and Constitution for the hit points. But not many characters need Intelligence. Usually you can get by with one specialist for that. And Strength can be dumped by a surprising number of builds, including combat builds relying on Dexterity. For that matter, only one skill depends on Strength. (And none depend on Constitution, but you still need the HP.) But a total of five skills depend on Wisdom.

I'd like to try to balance things out a bit better, with four skills for each ability, for a total of 16. I'd also like to have a few specializations available for each skills, which grant a bonus similar to expertise, but which can be tailored to fit the campaign.

Design Thoughts

Aside from the abilities, I'll need to consider the secondary stats, such as defense and hit points, and how those are derived. Here's my initial thinking:
  • Chance to hit depends on Agility, whether done with a bow or a sword or a spear
  • Damage depends on Fortitude, whether done with a bow or a sword or a spear
    • There may be some exceptions, with significant downsides. A dagger may depend on Agility for both damage and hit chance, but it doesn't do much damage. A firearm or crossbow may not depend on Fortitude for damage, but they have long reload times.
    • I base this at least partially on the fact that firing a bow requires a good bit of strength, which isn't reflected in D&D.
  • Defense (AC) depends on a combination of Mind and Agility (probably the maximum for most people, but some unarmored fighting styles may let you add these).
  • Health (HP) depends on a combination of Fortitude and Will. I'll probably sum these, as I favor a fairly high starting HP.
  • Spells can target any of these defenses.
  • Spellcasting can depend on Mind, Will, or both. I think it will probably be both for the pure spellcasters (Mind gives accuracy, Will gives damage), but may work differently for half-casters and others who have more stats they need to raise.
  • Many D&D skills can be combined. Lore will cover many kinds of knowledge. Investigation, Insight, and Perception may be covered by one Mind skill. Persuasion and Intimidation can be one Influence skill, and Performance and Deception may fall under the same skill. Specialization can give bonuses to certain sub-skills.
  • Rather than expertise, we may have the concept of specialization. That grants a +3 to a skill in a specific situation. When the Performance skill is used for a musical instrument, you may have a specialization.  Or a con artist may have specialization to his Performance in weaving a convincing lie. I'm thinking that each background may grant a specialization, as well as a skill.
  • I plan to apply degrees of success to everything, including attacks and spells. Getting a higher degree of success does more damage, or has a stronger effect for a spell.
    • For weapons, there will be no dice rolls for damage. Instead you add a fixed number between 0 and 5 representing the weapon damage to your Fortitude, and multiply that times your degrees of success to determine how much damage you do.
    • I haven't decided whether spells should have the caster roll, or the target roll, or both depending on the spell. When the caster rolls, the more degrees of success, the better for the caster; when the target rolls, the more degrees of failure, the worse for the target.

Skills

So let's summarize the skills I have in mind:
  • Fortitude Skills
    • Athletics - Running, jumping, swimming, climbing, all the things athletes do.
    • Labor - Farming, mining, digging pits, anything requiring long hours of backbreaking labor. From clearing collapsed tunnels to building a fortified camp, you'd be surprised how often this comes up in adventuring. And when you're not adventuring, there's always a need for strong backs.
    • Survival - Weathering harsh conditions, trekking long distances, and rousing from little sleep to do it again the next day. Includes finding shelter and water as you travel.
    • Steering - Sailing a ship, driving a vehicle, or riding a horse all require physical work to steer the vehicle or animal where you want to go.
  • Agility Skills
    • Finesse - From pick-pocketing to swapping the Gem of Doom for a fake while no one's looking, anything that requires fast hands falls under Finesse.
    • Stealth - Moving quietly, keeping to shadows, and slipping through crowds unseen. All of these fall under stealth.
    • Acrobatics - From balancing on a wire, to tumbling, to parkour, sometimes quick reflexes save the day.
    • Crafting - Making potions, magic items, armor, weapons, food, baskets. They all require careful handling and exacting detail.
  • Mind Skills
    • Mechanics - Locks, traps, the strange gnomish contraption that looks like it's about to explode. Understanding how things work often allows you to take it apart, and maybe even put it back together.
    • Observation - Noticing that you're being watched, spotting the secret door, hearing the beating heart under the floorboards, reading the expression of people and the tells of animals, all this falls under observation.
    • Lore - You read. Therefore you know stuff. Maybe even a lot of stuff.
    • Arcana - You're sensitive to the flow of magic, able to understand its currents and figure out what it does.
  • Will Skills
    • Concentration - Remaining focused despite distractions, and people trying to stab you--and sometimes succeeding.
    • Influence - Someone said the core of diplomacy is to talk softly and carry a big stick. Whether it's threats or promises, you're good at getting what you want. Applies even when dealing with animals and others who don't share your language.
    • Performance - Dancing, singing, playing an instrument, impersonating someone, or weaving a convincing lie. It's all about rejecting another person's reality and replacing it with your own. And if you're convincing enough, you can bring them along for the ride.
    • Profession - One might think that having a professional job like scribing or shopkeeping would require one to have a sharp mind. One would be wrong. The primary requirement of such a job is to be able to keep focused, remain polite, and endure the petty slights of customers, bosses, and colleagues, day in and day out.

Specializations

In addition to skills, players also have specializations. Specializations come from both the class, and from the background. For example, a bard could have a Music specialization in Performance, or someone with the farmer background could have a Farming specialization in Labor. Specializations cover specialized use of skills, and provide a flat +3 on top of the skill bonus. The specialization itself describes what conditions that additional bonus applies in, but ultimately it's up to the DM whether you can use your specialization bonus.

Most of these specializations are described in the backgrounds and class features which grant them, but the DM may allow additional ones. Here are some possibilities to give some ideas:
  • Athletics
    • Swimming
    • Climbing
    • Running
    • Jumping
  • Labor
    • Farming
    • Mining
    • Building
    • Digging
  • Survival
    • Arctic
    • Desert
    • Mountains
    • Forests
    • Plains
    • Cities
  • Steering
    • Sailing
    • Rowing
    • Riding
    • Piloting
  • Finesse
    • Pickpocketing
    • Legerdemain
  • Stealth
    • Nature
    • Darkness
    • Crowds
  • Acrobatics
    • Balance
    • Stunts
    • Traversal
  • Crafting
    • Alchemy
    • Smithing
    • Cooking
  • Mechanics
    • Locks
    • Traps
    • Steampunk
    • Vehicles
  • Observation
    • Empathy
    • Animal empathy
    • Tracking
    • Secrets
    • Alertness
  • Lore
    • Medicine
    • Religion
    • History
    • Nature
    • Military
  • Arcana
    • Spirits
    • Magic Items
    • Curses
    • Blessings
  • Concentration
    • Spellcasting
  • Influence
    • Animal Handling
    • Oratory
    • Intimidation
  • Performance
    • Dancing
    • Music
    • Acting
    • Deception
  • Profession
    • Scribing
    • Shopkeeping
    • Innkeeping
    • Trading

The Math

The fifth edition of D&D uses something called bounded accuracy. This limits how high rolls can get by keeping limits on the modifier, since the ability modifier maxes out at 5, and the proficiency modifier maxes out at 6, for a total of +11. Sort of. Then there's expertise, that doubles your proficiency modifier, spells like Bless and Guidance, that add 1d4, and Bardic inspiration, that adds d12. There's also the rogue's Reliable Talent, that causes any roll on the die below 10 to count as a 10. This means, at a minimum, a 10th level rogue with Reliable Talent and Expertise and Guidance and Bardic Inspiration, gets a total 25. On average, they would get about 35. That's a bit outside of bounded accuracy.

How would I control this? For one, I wouldn't grant expertise. I'll instead use specialization that will grant a flat +3 that doesn't scale with level. Second, abilities that would normally grant an extra die will instead grant an extra d10 roll that can replace one of the d10 rolls. (From the Weal pool, if we're using that. I'll probably make the pools an optional variant. If you're not using the pools, this is only limited by the class feature.) So while those will increase the average, they won't increase the maximum.

Otherwise, I'll scale similarly to how 5th edition does. Characters will receive bonuses to their abilities from their ancestry, background, and culture, but the maximum at 1st level for any ability will be 4. Until 10th level, the maximum will be 5, and until 20th, it will be 6. At 20th level, the maximum will increase to 7.

For the bonus from the skill, I think it will work similarly to proficiency bonuses in 5e, scaling with level. At first I was going to use the same scaling as D&D, 1 + level/4 rounded up. However, since I'm starting with a slightly higher ability modifiers, which increase to 7 rather than being limited to 5, and since my average rolls are higher by half (and my ~65% probability is about two points higher), maybe I'll just do level/4 rounded up. So skills will max out at 5, while ability modifier maxes out at 7.

Now, let's do some math, to determine what is Hard, Medium, and Easy for different characters. As a starting point, I consider something where someone has a 75% chance of success to be Easy, where someone has a 50% chance of success to be Medium, and where someone has a 25% chance to be Hard. Now with 2d10, we won't match exactly those numbers, but let's try to get relatively close. Players have a 55% chance to roll an 11 or higher, so we'll define that as our Medium. They have a 79% chance to roll an 8 or higher, but a 2% chance to roll a double 4 or double 5, which would effectively make those values below 8. So an 8 or higher will represent 77% chance of success. Meanwhile, a 2d10 has a a 21% chance of rolling a 15 or higher, +2% for the chance to roll a double 6 or double 7. So a 15 is a hard 2d10 roll, with a 23% chance of success.

So Easy, Medium, and Hard will represent a 77%, 55%, and 23% chance of success. Now let's define our characters:
  • Novice: +0 to the roll. No matter the level, no character's trained in everything, and most character's will have one dump stat that remains at 0. When that character is first to make this roll, that's what he does it with.
  • Average: +skill bonus to the roll. An Average character may have the skill, but doesn't necessarily have the ability score bonus.
  • Gifted: +max ability modifier to the roll. A Gifted character has a maxed out ability modifier, but no training in the skill. Often, he'll be the best choice to make the roll.
  • Skilled: +skill bonus + specialization bonus to the roll. Everyone has some specializations, but that doesn't mean that they're naturally talented with the ability. This assumes no bonus from the modifier, but Skilled can also represent someone with skill training and a decent modifier without specialization.
  • Adept: +skill bonus + max ability modifier. Some things you're just good at. The Adept has both the max ability modifier and the skill bonus, but doesn't have specialization. You won't always have an adept for every skill, but you'll count yourself lucky when you do.
  • Master: +skill bonus + specialization + max ability modifier. Then again, some people have it all. This is the best a character can get without relying on the fortune of Weal dice.
So first, let's consider what sort of rolls are Easy, Medium, and Hard for each character ability level. I selected levels 1, 5, 10, 15, and 20, since that covers are the skill bonuses and ability score maximums.

This gives us some idea of how easy it is to accomplish something. Even at level 1, what's Hard for the Novice character is Easy for the Master, and Medium for the Adept. A target number of 30, however, never ceases to be Hard, even for the Master. Such a task shouldn't be attempted without, at least, some favorable circumstances to help. And a 25 doesn't become Medium for the Master until level 20, and is still hard for the Adept.

In general, I think what's Medium for the Average character should be Easy for the Adept and should be Easy for the Master to achieve with an extra degree of success, and what's Hard for the Average character should be Medium for the Adept and should be Easy for the Master. I think this achieves that.

Where do attack rolls fit on this? Somewhere between Adept (characters are always skilled with their weapons, and usually max their attack roll as much as possible), and Master (as higher level characters tend to pick up magic weapons, that can give them a bonus close to the specialization bonus). Still, it's best not to design with Masters in mind, either for skill rolls or for enemies.

That does bring us to our design space for challenges. In general, I believe that an Easy target number should be Medium for the Novice character and Easy for the Average character, while a Medium target number is Hard for the Novice character and Medium for the Gifted character and Easy for the Expert, while a Hard target number is Hard for the Skilled and Medium for the Master.

Note that the standard 10/15/20 fits this fairly well for that level of difficulty. You can continue using that all the way up to high levels without leaving anyone behind, though it will start to become trivial to the Master, and pretty easy for the Adept. One way to handle that is to add higher levels of difficulty. Here's what I propose:
  • Target of 10: Easy Difficulty. Anyone can do it, and most people have a decent chance.
  • Target of 15: Medium Difficulty. It takes some luck for the novice to achieve, but every party should have someone with a decent chance of accomplishing it.
  • Target of 20: Hard Difficulty. A novice can pull it off. Barely. Most parties will have difficulty accomplishing it.
  • Target of 25: Expert Difficulty. If you have an Adept in your party, you might be able to pull it off, but it won't be easy.
  • Target of 30: Specialist Difficulty. Only the very best in the world can pull it off, and even they fail more often than they succeed.
Note that something that is Hard difficulty is Expert difficulty to achieve with an extra degree of success, and Specialist difficulty to achieve with two degrees of success. Setting the target of 30 means that your party probably won't manage it. But setting it to Hard, means they have a small chance of getting three degrees of success. Here are the probabilities for each of the character ability levels to accomplish these difficulties at levels 1, 5, 10, 15, and 20.

Sometimes, though, you want to know what will actually be hard for your party. For that, I suggest balancing around Easy for Average, Medium for Gifted, and Hard for Skilled. I personally find this useful for skill challenges, so I know what my players are generally able to handle.
  • Levels 1-4: 9 (Easy)/15 (Medium)/19 (Hard)
  • Levels 5-8: 10 (Easy)/16 (Medium)/20 (Hard)
  • Levels 9-12: 11 (Easy)/16 (Medium)/21 (Hard)
  • Levels 13-16: 12 (Easy)/17 (Medium)/22 (Hard)
  • Levels 17-20: 13 (Easy)/18 (Medium)/23 (Hard) 
This results in the following for the percentage odds of success (including the possibility of doubles, assuming I calculated them correctly):

Easy tasks remain Easy for the Average character (though they eventually approach Hard for the Novice character), Medium tasks fairly Hard for the Average character, and Medium to Easy for the Adept, and Hard tasks are Hard to Medium for the Adept, and approximately Medium to Easy for the Master.

Update (1/19/2023): Figuring out the math is of course an iterative process. I've created a new version based on two different assumptions: one where a Gifted (max ability, no skill) and Skilled (skill and specialization, no ability modifier) represent a more likely highest ability in the party, and one where the standard 10/15/20/25/30 are used throughout the game. 

Tuesday, January 17, 2023

Weal and Woe

The recent kerfuffle over the Dungeons and Dragons OGL has me wondering whether I can turn my 2d10 conversion of D&D into its own stand-alone, non-OGL system. There's a lot I would need to do to make that work, but let's start with the advantage/disadvantage mechanic. I want to take a system where you can add d10s to 2d10 rolls, but universalize it and limit it. So to that end, let's introduce the idea of the Weal and Woe dice pools:

The Weal and Woe Pools

The universe is strangely balanced, whether by gods, some unknown purpose, or just random chance. Good luck always follows bad, and bad luck follows good. In the game, this is represented by the Weal and Woe dice pools. While dice are more tactile and intuitive to use for these pools, tokens, coins, tallies on a sheet of paper, or a tracker on a virtual table top may be used instead.

At the end of each rest, each pool starts with 5 d10s. After a player rolls 2d10, there are circumstances where he or other players may roll an additional die from the weal pool, or where the GM may roll an additional die from the woe pool. No player (including the GM) may roll more than one die from his pool for any 2d10 roll. After all dice are rolled, the players (including the GM), in the order that they rolled their dice, select one of the rolled dice (including the original 2d10 dice) and place that die in the opposite pool from the one they drew their die from. The remaining two dice are the final roll.

If any final 2d10 roll (after any Weal and Woe dice are added and the selected dice are sent to their pools) is a double, and that doubled number is greater than the amount in the Weal pool (if a player is rolling the 2d10) or the Woe pool (if the GM is rolling the 2d10), then move a die from the opposite pool to the 2d10 roller’s pool. So if there are five dice in each pool, and a player rolls two 6s, move a die from the Woe pool to the Weal pool. This has the effect of balancing the pools over time.

The circumstances where players may roll dice from the pools are the following:
  1. Before the player rolls his 2d10, the GM may declare that the circumstance is either favorable or unfavorable. With a favorable circumstance, the player may choose to roll a die from the Weal pool after his roll, and select a die to discard to the Woe pool. With an unfavorable circumstance, the GM may roll a die from the Woe pool after the roll, and select a die to discard to the Weal pool. Alternatively, if it's an enemy who suffers an unfavorable condition, the player may roll from the Weal pool to cause him misfortune, and an enemy with a favorable condition gains his extra die from the Woe pool.
  2. Players may select to aid another player. To do so, they must have training in the skill, or another ability relevant to what the other player is attempting. They also must forgo making an attempt themselves, and share in the consequences if the final roll is a failure. The duration over which the helper can’t make an independent attempt depends on the situation. You can help someone else make an attack by feinting, but you can’t make an attack in the same turn. You can help someone climb a wall, but you can’t make progress climbing the wall yourself at the same time. If you’re trying to help someone recall some lore, or figure out a mechanism, it’s assumed that you’ve already given it your best shot, and you can’t try again until they can, when the circumstances change—you gain access to a new tool or research materials, for example.
  3. Certain ancestral, class, or other features may allow you to draw from the Weal pool either to help in your own 2d10 roll or an ally’s. On the other hand, certain monster abilities allow them to draw from the Woe pool.
It’s certainly possible for a party or the GM to burn through their pool, especially when they’re desperate. However, once one pool fills up to 10 dice, new options are on the table. At any time when the players have 10 dice in their Weal pool, or the GM has 10 dice in their Woe pool, the party (all players must agree) or GM, whichever has all the dice, can do one of the following:
  • The party or the GM declares that every roll for one side in the combat has one higher degree of success, and every roll for the other side has one lower degree of success, than the dice actually show, until the beginning of the turn of the character when that is declared (I'll discuss how degrees of success work for attacks later).
  • The party or the GM declares that a single roll is a double 10, no matter the circumstances of the roll.
  • A party or GM can describe a lucky break, introducing a circumstance or random chance brought on by the preponderance of luck on one side. The GM may start a random encounter with a deadly foe, a player may declare the arrival of a strong ally. The circumstances of the lucky break doesn’t last beyond a single encounter.
Once the GM or party uses the dice in this way, all dice are divided equally between the two pools again immediately (after the perfect double 10 roll, but before the encounter or round plays out).

Design Goals

I like the idea of advantage and disadvantage, but I think I like it more when it's a renewable but limited mechanic. When that's the case, people are more careful about using it. If you can attack with a Weal die every turn, you're going to think twice when you start to run low, especially when there's a chance you can give the enemy all ten dice that lets him do something particularly powerful. There's an element of risk in using either Weal or Woe, especially when you're running low and there's a chance you can give the other side the last die he needs to have all ten. Even if you save the last die, he may eventually roll a double 10.

On the other hand, once you have all ten, you have a motivation to use them quickly, because otherwise the first double the other side rolls (there's a 10% chance every time someone rolls 2d10) will steal that die. Since the fewer dice in your pool you have, the more likely a double is to move a die to your pool, the system tends toward balance. (I suspect it will trend toward the Weal pool, just because the players roll more 2d10s, but that gives them a motive to spend more Weal dice too.)

I think this feels most natural when the pools contain actual d10 dice. Then you move a die from your pool, roll it, and, when it's time, put a die in the opposite pool. It's very physical, moving dice around on the table. I also like that when you help (or hinder) someone, you roll the helping/hindering die yourself, and then decide which die you remove--you don't feel shorted by someone else's poor rolls, as you're taking part in the rolling.

Finally, by letting the player and the GM decide which dice to remove, I don't feel like I need to come up with an algorithm, like I did for rolling with advantage and disadvantage with 2d10 (especially when I programmed it into Avrae). I was originally going to decide who removed the dice in which order (2d10 rolling player? GM? Other player? Should they alternate?), but I think it works best doing it in order of rolling the extra d10, but waiting until all dice have been rolled. That way if you decide you want to add a Weal die, there's always the risk that even if you roll better, the GM will take it. That will mitigate the number of dice rolled for any 2d10 check. I didn't set a hard limit on the number of dice you can roll--obviously you can't roll more than twelve, since at that point all the pools are used. But since each player is limited to 1 die, it would have to be a pretty big party to make that happen, and you'd be giving up almost all the dice to the GM (or all of them, if he didn't roll one).

One thing to note is that, as dice move from one pool to another, people's personal dice can go into a pool. People should probably have different colored dice if they want to make sure they get their dice back. I'd also allow them to trade a d10 for their personal die in one of the pools.

Example

There are two dice in the Weal pool, and eight in the Woe pool. The rogue is planning to climb a wall, but it's dark, and as a human, he can't see in the dark. The GM declares that he has an unfavorable circumstance. The fighter and the ranger are both skilled climbers, and importantly, can see in the dark, so they declare that they will help the rogue up the wall. The GM rules that they can, but they can't climb the wall themselves until the rogue's climbing is resolved, and if he falls, he'll land on them and they'll take damage as well. The players agree, and the rogue starts climbing.

The rogue rolls 2d10, and gets two 6s. A high double! The GM decides to spend a die from Woe, and rolls a 2. Seeing this, the fighter rolls a die from Weal, and also gets a 2. The ranger notes that their Weal dice pool is running dangerously low, and opts not to roll, hoping that it'll be good enough.

The GM removes a die, taking one of the 6s and putting it in the Weal pool. Then the fighter removes a die, and places one of the 2s in the Woe pool. The rogue is left with a 2 and a 6, or 8 plus his modifier. If that's not enough and he falls, the ranger may regret his choice when the rogue falls on him and the fighter!

Later, when the ranger decides to stealth ahead, he rolls 2d10 and gets two threes. A low double and one degree of failure, but since the doubled number is higher than the two dice in the Weal pool, one die is transferred from the Woe pool to the Weal pool. Now it's three dice in the Weal pool and seven dice in the Woe pool.

Saturday, December 31, 2022

Dungeons and Dragons with 2d10

If you've played Dungeons and Dragons, then you know that the basic dice mechanic is a d20. You roll a d20, add a modifier, and compare that result to a  Difficulty Class, or DC, for a skill, or the Armor Class (AC)  of an enemy, to determine whether you succeed or fail.

There are three types of d20 rolls in D&D: attack rolls (attacking an enemy with a weapon, your bare hands, or certain spells), saving throws (to prevent spells and other bad effects from happening to you), and ability checks (everything else where you want to accomplish something and there's a chance of failure). Rolling a natural 1 (a 1 shows on the die) or a natural 20 (a 20 shows on the die) has a special effect only for attack rolls: natural 1 always misses, and natural 20 always hits and does extra damage. There are a few other places it matters (halfling luck allows you to reroll any natural 1), but many D&D tables houserule additional effects of a natural 1 and natural 20.

The d20 gives a nice, flat probability distribution. You're as likely to roll a 1 as a 20 as a 10. For that reason, it's exceptionally swingy. In many situations, this doesn't matter. If a lock has a  DC of 13 and a rogue has +5 with his thieving tools, he has a 65% chance of succeeding. If he rolls a 1 or a 20, he usually doesn't succeed or fail more.

Where that swinginess can produce weird results is with opposed rolls. Let's say your skinny rogue is wrestling  with an ogre. The rogue has a -1 on his grappling check, while the ogre gets +4. You would think that the rogue wouldn't have a chance. But because of D&D's famous swinginess, he gets a 26% chance of outwrestling the ogre. That's a lot considering there's a +5 difference.

Many games reduce the swinginess by using dice pools. For example, the Powered by the Apocalypse game engine uses a 2d6 dice pool. GURPS and AGE use a 3d6. 3d6 gives a nice bell curve with results from 3 to 18, centered on 10.5. The problem is that with a standard deviation of 2.96, 67% of the rolls will end up between 8 and 13. The chance of rolling an 18 or a 3 is only 0.5%. In short, it's too narrow a distribution. If you wanted to use 3d6, you'd have to adjust all the bonuses and DCs to make it work.

However, a much more reasonable result can be achieved with a 2d10 roll. For comparison:

Probability distribution curves for 1d20, 3d6, and 2d10. Courtesy of AnyDice.

While the 2d10 has a sharp peak at 11 (slightly off from the 10.5 average of the d20 and the 3d6), it's not as sharp as the 3d6. This means it's more likely to roll higher or lower.

The best way to see this is not a probability distribution chart, but looking for the chance to roll at least a number, as shown below.

Probability of rolling at least # for 1d20, 3d6, and 2d10. Courtesy of AnyDice.

In D&D, a difficult check is one where you need at least a 15 to succeed. Players are usually cautious about attempting rolls that require a higher roll than that. With a d20, the odds of succeeding against a 15 is 30%, while with 3d6, it's less than 10%. With a 2d10, the odds are 21%, which I consider a decent compromise.

Now, let's consider the odds of rolling an 8 or higher. This is generally the to-hit number needed to hit an enemy with average AC for the players' level. Under 1d20, the odds of hitting are 65%. With 2d10, it's 79%, and with 3d6 it's 84%. Here we see that 2d10 and 3d6 are much closer to each other than to d20, but a higher average to-hit chance for players is actually an argument for this system--very little is as disappointing as missing in combat.

So let's see how we would do this conversion.

Simple Conversion

Considering all this, how do we implement a 2d10 system in D&D? Simple, any time you roll a 1d20, you substitute a 2d10 instead. If you are doing something that gives you a reroll or extra roll (advantage, disadvantage, luck), you roll 2d10 twice, and take the one (higher or lower) that fits the requirement.

But what about natural 1s and natural 20s? You can't roll a natural 1 anymore, and you roll a natural 20 only 1% of the time. It would be disappointing for critical hits to happen so seldom.

For this we introduce the idea of doubles. If you roll the same number on both d10s, and they are five or less, this is a low double. Count that as critical miss for an attack roll. If you roll the same number on both d10s and they are six or more, that is a high double, count that as a critical hit for attack rolls. Importantly, a natural 1 and natural 20 are not an automatic failure or success except for attack rolls in combat. 

We can also use low doubles for abilities that let you re-roll when you roll a natural 1 (for example, halfling luck). Instead substitute low double for natural 1 in that rule. But a low double isn't a 1. If you roll two fives, that's a 10, and it's more of a gamble to reroll that than to reroll an actual 1 any place but for attack rolls, where two fives are an automatic failure.

In addition to this simple conversion, there are some optional rules you can add.


Optional rule 1: Doubles and Degrees of Success

Many DMs allow for degrees of success and failure for ability checks. If your result (roll + modifier) is 5 more than the DC, you are more successful than if you just met the DC, and if your result is below 5 less than the DC, you fail more. A table of degrees of success would look like this.

Roll rangeDegrees of Success
DC+10 <= result3 degrees of success
DC+5 <= result < DC+102 degrees of success
DC <= result < DC+51 degree of success
DC-5 <= result < DC0 degrees of success
DC-10 <= result < DC-51 degree of failure
result < DC-102 degrees of failure

What degrees of success or failure means depends on the DM and the context of the roll. Here are some possibilities:
  • For any sort of knowledge or information check (Arcana, Nature, Survival, Perception, History, Religion, Investigation), the higher your degree of success, the more information you obtain. However, more degrees of failure might actually make it harder for others, as you trample over important clues or confuse your party members with your misinformation.
  • With three degrees of success, you don't just climb a wall, you clamber up it at full speed and give anyone following advantage on their climbs.
  • With two degrees of success, you climb up at half speed as usual, but those who follow you have advantage on their climb checks.
  • One degree of success is just success. 
  • Zero degrees of success is a failure, but it's a near miss. The DM can allow you to try again without penalty, or even allow you to succeed for a price: it takes longer, or you alert a guard, or you gain a level of exhaustion, or you convince the guard to let you through but you need to bribe him.
  • With one degree of failure, you not just fail, you lose ground, so if you can try again at all, it's going to be harder. You fell if you were trying to climb a wall, or you insulted the person you were trying to persuade.
  • With two degrees of failure, the task just became impossible, and you're going to have to try another way. You jammed the lock and can't pick it now, or the pipe you were trying to climb collapsed.
Importantly, not all ability checks need to have degrees of success or failure. Some can be a simple pass/fail, no extra benefits or consequences for more or less degrees of success. But degrees of success or failure give us options, many of which DMs already use a lot of the time. 

With a 2d10 system, degrees of success become more significant, as you're less likely to roll really low or really high, so more degrees is more extraordinary. Importantly, with degrees of success, we can apply high and low doubles to ability checks without turning a double into an automatic success or failure. With this option, a high double increases the degree of success by one, while a low double decreases the degree of success by one. This is equivalent to adding five for a high double and subtracting five for a low double.

We can even circle back to attack rolls, and apply degrees of success to them. In this case, a result  5 higher or lower than the AC does not grant an extra degree of success or failure, but rolling a high or low double does. A critical hit requires two degrees of success--you need to roll a high double, but you also need your roll plus modifier to be above or equal to the AC. A high double plus modifier that's below the AC hits, but doesn't critical. Likewise, a low double can turn a hit into a miss. As an option, you can also use 1 degree of failure (a low double plus modifier that is also below the AC) as a fumble. Note that there are generally no fumble rules in fifth edition D&D, so use that with caution. (If I used it, I'd grant an opportunity attack to enemies when a character fumbles.)

Finally, we can apply this to saves as well. A high double automatically saves, a low double automatically fails. If we really want to, we can turn a low double that is also below the DC into a critical failure (take double damage from the spell or effect) and a high double that is also above the DC into a critical success (take no damage if you would have taken half), but again, use with caution. The  rogue's or monk's Evasion ability with this particular variant is equivalent to one extra degree of success for Dexterity saves. 

When we allow high double and low double to both be meaningful, keeping the higher roll or the lower roll with advantage or disadvantage can become confused. For the sake of simplicity, the higher degree of success is the roll to keep with advantage, or discard with disadvantage. In most cases, a high double beats a higher roll beats a lower roll beats a low double. But there are exceptions: a double 5 is better than a 1 and a 2 for ability checks, but not for attack rolls and saves, where a double 5 automatically fails but a 3 plus a high modifier might succeed.

Optional rule 2: Extra Dice

In the simple conversion, we attempted to keep advantage and disadvantage the same--just roll 2d10 again. Let's revisit that. What if, instead of rolling 2d10 twice, we rolled 3d10 and picked the two dice we wanted for advantage, or discarded the highest die roll for disadvantage?

Probability of rolling at least a value for advantage and disadvantage variants, ignoring doubles. Courtesy of AnyDice.

You'll notice right away that for the probability to roll at least a value, the difference between 3d10 pick the highest or lowest differs very little from the best of two 2d10 rolls. The difference between those advantage calculations and the regular d20 advantage is also pretty small. There is a marked difference between disadvantage with 2d10 and disadvantage with d20, though, for complex mathematical reasons that I won't go into because I haven't figured them out yet.

What's the reason we might want to use an extra d10 instead of more 2d10 rolls? For one, it makes advantage and disadvantage easier--always choose the high double, never choose the low double with advantage. For example, if you rolled two 5s and a 1, a 1 and a 5 is always better than a low double 5, no matter the type of roll (6 > 10-5). For disadvantage, it's the inverse, though I find it simpler to discard the highest and not worry about doubles--players are less likely to feel cheated if that happens to remove a low double or result in a high double. 

It also makes double and triple advantage or disadvantage easier to adjudicate--just add more d10s. For the most part, double and triple advantage don't exist in Fifth edition, but there are exceptions, such as the Elven Accuracy feat and the Lucky feat. For Elven Accuracy, roll 4d10 (advantage + 1d10) and choose two d10s. For every luck point spent on a roll, you can add another d10, but you always choose two d10s.

But what if you have disadvantage and use a luck point? Lucky doesn't have to cancel disadvantage in this case. Instead you roll 3d10 for disadvantage, then 1d10 for the luck point, remove the highest d10, and pick two of the remaining d10s. This way lucky no longer converts disadvantage into super advantage, but it can still help to mitigate it.

Finally, if more than one person can reasonably use the Help action to help another in a roll, then you can add a d10 for each person helping.

However, for features like halfling luck or a Divination Wizard's Portent, where you replace a roll rather than take the highest or lowest roll, you roll a fresh 2d10 instead of adding a d10. (RAW, you don't keep any advantage or disadvantage that the roll would have.)

Optional rule 3: Inspiration

Finally, what about Inspiration? Here, I favor borrowing from the most recent One D&D playtest (these are playtest rules for the next version of D&D). In this version, you can spend Inspiration to grant yourself advantage after rolling. If you rolled with disadvantage initially, you don't just cancel the disadvantage--you convert it to advantage. This works whether you roll 2d10 twice (pick the best rather than the worst) or 3d10 (don't discard the highest before picking two dice). Otherwise, you roll an extra d10 or roll 2d10 again. But you can't use inspiration if you already have advantage.

The thing I would change is that instead of gaining inspiration when you roll a 1, you gain inspiration after the final result of your roll is a double--either high or low. (I say "after the final result" to make it clear that you can't use the inspiration you gain on the same roll that grants it to you.) It represents both determination to do better after stumbling, and riding the high of success. (This also means that a feature like halfling luck doesn't make it almost impossible to gain inspiration from die rolls.)

Summary

If you apply all these optional rules, the end result would look something like this:
  • High double: Both d10s have the same value of 6 or higher.
  • Low double: Both d10s have the same value of 5 or lower.
  • Ability Check: roll 2d10 + modifier (high double adds 5, low double subtracts 5)
  • Ability Check Degrees of Success/Failure: For every 5 above or below the DC, you get an additional degree of success or failure, respectively. What this means depends on context.
  • Saving Throw: roll 2d10 + modifier (high double always succeeds, low double always fails)
  • Attack roll: roll 2d10 + modifier (high double always hits, crits if would hit anyway, low double always misses)
  • Advantage: roll 3d10, pick two (it's always advantageous to pick high doubles and avoid low doubles, otherwise pick the highest two d10s)
  • Disadvantage: roll 3d10, drop the highest.
  • Inspiration: Gained when roll any double final result. Can be spent after roll to turn into advantage (even if initially rolled with disadvantage), roll an extra d10 if necessary
  • Luck point: Roll an extra d10, pick two d10s. (If initially rolled with disadvantage, still remove the highest roll before picking two.)
My group has decided to playtest these rules. We're playing the Icewind Dale: Rime of the Frostmaiden module, so I'm interested in seeing what effect this has when no changes are made to the module to adjust for this.