Classless OSR Conversion

I've been toying around with a few ideas for making a classless OSR game.  Not something like Knave where anyone can do anything and magic is all item-based, but something where you have unique abilities that are a) inherent to your character, not coming from an item, but b) coming from something other than classes.

Here's one such idea.  The core concept here is that characters are defined mainly by ability scores, with high ability scores giving access to some special abilities.  This is a hack you can add onto the class-based OSR game of your choice.

This converts your game of choice into something very free-form where player characters can sort of mix and match class abilities to create really unique characters.  It also means, though, that power differentials between player characters can get bigger than is typical for OSR games.

Ability Scores

To make ability scores more important, you'll have to make the range of modifiers higher than is typical for an OSR game.  Something like:

1-3: -3
4-5: -2
6-8: -1
9-12: 0
13-15: +1
16-17: +2
18-19: +3
20: +4

Additionally, since we're getting rid of classes, saves need to be ability-based, not the old school poison wands, breath weapon, etc.  These work like in GLOG or The Nightmares Underneath: roll a d20 under the appropriate ability score.  DEX for dodging stuff, STR to resist being pushed, INT to see through illusions, etc.  Rolling equal to ability score is a failure, because ability scores can get up to 20.

Every time you level up, pick two ability scores to test for advancement.  Roll a d20; if you roll over the score's current value, it goes up by one.

High ability scores can also give you special abilities– more on that later.

Note that because ability scores are important, you need some rule for allowing people to not have to play characters with really low ability scores.  Either let them re-roll terrible statlines like in Lamentations, or raise one low ability score to 14 like in most of Kevin Crawford's games, or reverse all of their ability scores like in Esoteric Enterprises (replace all of them with 21 minus what you rolled, so 7 becomes 14, etc).  Don't be too generous though; high ability scores help players A LOT.

Hit Points, XP, and Other Nuts and Bolts

Since there are no classes, everyone gets d4 HP per level, max HP at level 1.  Yes that's low; there will be ways to get more.  You could make that d6 though, if you want characters to be sturdier.  CON may or may not apply to hit points; that's up to you.  

If your base system has different classes level at different rates, everyone levels as a fighter.  

If your base system uses race as class, then you need to convert that to race and...well not class, but you'll see.  Apply some kind of XP penalty to demihumans to account for their extra abilities; maybe they level at whatever rate they'd normally level at for their race, maybe not quite that bad, maybe worse.  This could be hard to balance honestly, so this whole hack works best if you apply it to a system that doesn't use race as class, or just borrow race traits from another system.  

All characters are proficient with light and heavy armor, shields, and all weapons.  Plate mail, or heavy armor, is the only thing only some people will be able to use.  

Ability Perks

Aaaand here's the fun part: the mix and match abilities we'll replace classes with.  High ability scores allow you to choose "ability perks," which replace class features.  

So for example, you could get an ability perk for each ability score equal to or higher than 12, a second if an ability score hits 15, and a third if it hits 19.  If you wanted to be a little stingier with the perks, you could award them at 14, 17 and 19.  Or you could split the difference and go with 14, 17, 19, or even 14, 17, 20; that makes a 20 really awesome but also incredibly hard to get.  

Rolling up a bunch of random characters, it looks like the first set of thresholds gives the average starting character 3 perks, and the second allows 1.5.  Regardless, don't set these thresholds at ability score values where the modifier also goes up; make it so most ability score values over 12 are giving you either a perk or a higher modifier.  

So taking the first set of values, if you had STR 15, DEX 13, and WIS 14, and the other scores were below 12, you could pick two strength perks, one dexterity perks, and one wisdom perk.  Perks are, as mentioned, the class features from your game of choice (or other games, or ones you just make up), now mixable and matchable.  

Charisma

-Animal companion, like a ranger 

-A squire, apprentice or servant, who doesn't need to be paid beyond room and board, is very loyal, with class level equal to half of yours rounded down.  Can be replaced in a week or so if they die.

-Lay on hands, as a paladin

-Turn undead, or whatever the spiritual enemy of your god is

-Get a totally sweet magic horse, like a paladin

-Attract follower and build a stronghold, if you think attaching the domain game to class features is cool (it isn't)

Constitution 

-Get an extra hit point per level.  Applies retroactively, can be taken up to 3 times.

-Immune to all diseases, like paladins

-There aren’t a lot of good perks for CON, I’m open to ideas here
-You can hold your breath for up to an hour.  This makes you immune to inhaled poisons only if you have a second or two of warning to hold your breath. (From Phlox on the OSR Discord server)
-You only need to sleep four hours a night.  You can also get a full night's rest in one hour, once, but can't do that again until you've made up for it by sleeping eight hours in a night.  (From Phlox again)
-If you successfully save versus an ingested poison, you can re-purpose the poison by spitting it at an enemy, biting or scratching them, forcing them to save or be poisoned.  (Phlox again)

Dexterity

-Thief skills as a thief of half your level.  Can be taken a second time to get skills as a thief of your level.  Could also be taken as an INT perk in systems like Lamentations where skills include things like medicine, tinkering, languages, etc.

-Fast movement and slow falling as a monk.

-Get a bonus unarmed attack plus an extra one per five levels, as a monk

-Ranged attack bonus as a fighter

-Double damage and +4 to attack when backstabbing, if that’s separate from the rest of the thief skills

Intelligence

-Cast spells as a wizard of half your level.  Take a second time to cast as a wizard of your level.  Casting in any armor heavier than light armor is either impossible or requires a roll.

-Have a chance to use magic items you don’t qualify for, like a thief

-Poison and disguise, like an assassin

-Trained herbalist/alchemist or something like that

Strength

-Melee attack bonus as a fighter

-Plate/heavy armor proficiency

-Rage as a barbarian (could be CON instead maybe)

-You can carry twice as much stuff

Wisdom

-Cast spells as a cleric of half your level, plus you’re an ordained priest.  Take it twice to cast as a cleric of your level, and be somehow prominent in the church.

-Cast spells as a druid of half your level, only if not wearing metal armor, plus speak druidic and whatever minor abilities druids get at level 1.  Take twice to cast as a druid of your level, plus get whatever minor abilities druids get at higher levels (not shape changing).  

-Shapechange as a druid, only if not wearing metal armor.

-Tracking and alertness as a ranger

Final Thoughts

This would work well applied to something like Lamentations, OSE, Esoteric Enterprises, Swords and Wizardry, or The Nightmares Underneath.  It has some trouble accommodating race as class; you can do it but have to make some judgement calls.  It also seems like it would be harder to apply to something like Perdition where classes have a bunch of features that you get to pick from.

There are a few balance issues I'd like to work out.  Starting ability scores are incredibly important, so I might want to smooth them out a bit more.  

There also seems to be too little incentive to try to advance low ability scores when you level; yes they're more likely to advance, but they're nowhere near giving you a cool ability.  I might want to make it so ability scores with a negative modifier actually advance two points if tested successfully, and one if the roll fails.  

But other than that, this seems like it would be super fun.  I'll probably try it in one of my games.

After hearing Stephen's feedback in the comments and thinking it over more, I've come up with the following modification that seems a bit more fair: the number of perks you get is based on your level, but which ones you have access to are based on your class.  

You get two perks at level 1, and an additional one at levels 3, 6, 10, 15, 21, etc.  

The perks are still linked to ability scores, but they merely limit how many you can pick from a given ability score.  So if you have CON 12 you can pick one CON perk, if you have INT 15 you can pick two INT perks, etc.

However, you can also completely ignore that limit for your highest ability score, however high it is.  If you get all of the allowed perks for that score somehow, you can ignore it for the second-highest score.  

So now, ability scores channel you towards doing what you'd logically be good at, but the power differential between high and low scores isn't massively increased.  I'd still keep the widened modifier range and testing for ability score improvement though.