Ascending Ability Checks?

So we’re playing OSE, using ascending armor class. When attacking, players want to roll high. And when rolling saving throws, players want to roll high. But when making ability checks, they want to roll low. Now, I’m not opposed to ‘roll low’ at all, but it seems like with just one of three core mechanics inverted, players often get confused and have to double-check the logic almost every roll. I don’t think having mixed logic adds anything awesome or old-school feeling to the game, just confusion.

Now, we could go full descending rolls, and that’s fine for DAC; but then ‘lower numbers are better AC’ becomes a thing, which I have always found unintuitive (even back when 2E was the current version). And saving throws are still ascending…

So how about making ability checks ascending too? Just subtract your ability score from 21 and that’s your target number/DC, modified for difficulty by the DM. I imagine this has been done before, but I haven’t ever seen it mentioned.

Anything problematic?


I see what you mean. Your idea isn’t problematic mathematically, but you would have to adjust the scores every time. And humans are not very good at subtracting fast. If you adjust the ability scores permanently it also becomes unintuitive. With lower scores meaning the PC is better at it. To be fair that is how saves work and it seems fine.

In OD&D you would roll high against a target DC without mods most of the time (maybe +1, rarely +2). So you could do that, where you assign an appropriate target number and that the player tries to beat rolling high, regardless of ability scores and without modifiers (+1 or +2 if very appropriate). I think I would go with this variant. But it does render the ability scores kind of obsolete. Maybe you could assign the existing modifiers (the NPC reactions of CHA for example) for all rolls with that attribute, not only what they are supposed to be assigned to. This way you get bonuses from -3 to +3.

There is also a possibility of assigning ability bonuses to each ability and counting roll+bonus over 15 as a success. That is how Knave does it, where your ability bonuses are just the ability score -10. I’m not sure about the math, but it shouldn’t break the game too bad (I hope). This does add another layer of complexity to an already complex system (and the abilities have their own modifiers too).

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I agree with the diagnosis 100 percent. It’s confusing. I play D&D with newbs a lot and I end up having to draw up arrows on the saves and down arrows on the stats.

I wonder if we still need saving throws. I think 5th Edition got rid of them? They’re pretty damn abstract and I think served mostly as class balance. For many modern games, class balance isn’t as big a deal and pretty much all saving categories can be replaced by attributes.


I see what you’re saying; you would need to do the ‘subtract from 21’ every time (unless you just wrote the result next to each score, such as 15[6] where 15 is your score and 6 is your DC). Maybe that would simplify it a bit?

I really like the idea of Knave’s “each point above ten is a +1 bonus” but all the versions I have of Knave don’t show that as the ability mechanic… must be in some other revision.

5e still has saves. Nobody ever uses them from my experience. :slight_smile:

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The one thing about saving throws is they represent survivability of the character. You can have terrible ability scores but your dwarf is always going to be pretty tough because of their saving throw values not being tied to their ability scores.


Writing 15[6] seems like the same problem as having descending AC. Now you have 2 numbers that represent the same thing. And having a lower number mean better ability is counter-intuitive.

Edit: But I would still test it with players, and see if this helps them or not.

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I came in to suggest this. Presumably you could just use the standard OSE attribute modifiers, and set a standard target across the board of something like 14+ or around that. If it’s a particularly easy / hard task, roll two dice and take the highest / lowest. What you lose in granularity is made up for in simplicity.


@KnightOwl @Max

5e uses Saving Throws, but they are more tied to your Ability Score modifier and a bonus given to the character based on their class and level. Rather than have categories like in OSE, AD&D or B/X; the spell system from 5e uses a simple DC-based off of 8 + Prof bonus + Spellcasting modifier with the target of the spell effect rolling against that DC to see if they pass or fail. This generated DC is used for all saving throws related to spell casting regardless of the effect.

5e saving throw works okay for what it does, but it doesn’t reflect the kind of resistances and abilities that say a Dwarf or Barbarian should have when going up against certain spells or effects. It feels a little bit too clean and doesn’t really help since certain saves should be cakewalks while others are harder for those same classes.


To respond to your original post, you might want to try out using a system where you take the Standard DC and lower it by subtracting the Ability Score/Attribute bonus that PC might have. Since that would be the DC/Target for an average task, you can make a Standard Easy (super low DC), Medium (higher than the Standard DC) and Hard (much higher than the Standard DC) DCs for a quick reference for certain classes to reflect their advantages and disadvantages.

It’s a half baked idea so I’m not sure how well this will work since I just thought of that now.


What about turning saving throws to roll-under as well? Simply invert them to the other side of 10; e.g. a saving throw value of 8 would become a 12, a 4 would become a 16.

It would eliminate the confusion between saves and checks and it’s pretty easy to remember that an attack roll needs to be high.

I think it’s is a little more elegant than subtracting your ability score from 21.


How about d20 + ability score >= 21? It’s mathematically the same, it requires no extra space on the character sheet, and it preserves the notion that higher numbers are better.


Good idea. I have one tiny nitpick though: this means constantly adding double digit numbers. (extra brain practice I guess).


There will always be a trade-off, whether it’s

  1. sometimes you need to roll high, sometimes low
  2. sometimes higher characteristics are good, sometimes lower
  3. addition or subtraction
  4. the hassle of rewriting all bits of the game
    You gotta pick at least one :stuck_out_tongue:

Oh, that’s interesting… I do like that notion. A target number of 21 is somewhat memorable too since it’s the same as trying to hit blackjack.

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I’m no mathematician so maybe I’m missing something. But in B/X, at least, most characters start with at least a few 15s, or about a 75 percent chance of failure.

If the average ability score is 9-11, then they’d only need to roll a 10 (ish) to succeed. It seems closer to 50/50 to me. I’m okay with that, probably, but it doesn’t seem the same. Unless, as I said, I probably missed something.

Also would you drop the difficulty number needed as you leveled up? Levels 4-6, need a 19, Levels 7-10 only need to reach a 17 kind of thing?

I like this enough to wonder why none of the retro-clones or waves of OSR has written their saves this way.


(Hm, it seems like my reply was eaten earlier. Good thing I left the txt file open.)

Well, the idea was to replace roll-under mechanics. To wit, rolling under (or equal to) 15 on a d20 has a 75% chance, and d20+15 also has a 75% chance of being equal to or greater than 21.

I’m personally not a huge fan of improving ability checks based on levelling (I think that level-based advancement ought to be class-specific). If you do want to implement it, however, it would be easier to introduce ability score increases directly.


Yeah this is a good idea. Make everything roll under. Still have descending AC then, but at least it’s all consistent!

Most systems with the roll-above saving throws don’t actually employ the roll-under ability checks (if they do, it’s always marked as an optional rule).

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Yeah this is true; ability bonuses become a thing and then you get DCs.