I must create a system, or be enslaved by another man's. I will not reason and compare: my business is to create.

- William Blake

Friday, November 06, 2015

A new method for BD&D skills

I have spent a few posts explaining why I dislike the "modern" D&D method of rolling 1d20 + mods for skills. Basically, I think it doesn't work; take a look at that post if you disagree, and I would be happy to hear you out.

 Some "old school" inspired methods are obviously better in some regards - 1d6+mods, 2d6+mods, 3d6 roll under, 1d20 roll under, etc. The problem is, you must introduce a new mechanic, DCs, roll low, modifiers, etc. Not a big issue - I prefer adding new mechanics than using some alleged "unified" system that doesn't work for me - but, of course, I like multipurpose mechanics and would rather use an existing one if I can.

There are some good candidates already - the 2d6 reaction table, the thief's 1d6 and d100 skills, etc. Using 1d6 with modifiers (1-2 for hard tasks, 1-4 for easy tasks, etc), or Xd6 roll under (3d6 for ordinary tasks, 4d6 for hard tasks, etc), is also a good idea.

But now I want to propose something else: using ability scores modifiers as the DCs/TNs (Difficulty Class, Target Number, etc).

As you know, Basic D&D uses something similar to this for abilities:

Score Modifier Description

3 -3 Abysmal

4-5 -2 Terrible

6-8 -1 Poor

9-12 0 Average

13-15 +1 Fair

16-17 +2 Good

18 +3 Great

The system I propose uses the modifiers above as DCs.

For example, a "great" feat of strength would have DC 3. A simple, "average" task will be DC 0. If your ability modifier is equal or greater than the DC, you will usually succeed.

To meet the DC, you rely on two things simultaneously:

a) Your ability modifier;
b) A 3d6 roll that generates another modifier (from -3 to +3) in the same way you ability does.

The sum of a) + b) must be equal or greater to the DC for you to succeed.

It's basically Dice + Modifiers versus DC, with a twist: the dice will generate a result between -3 and +3 instead of 3 to 18.

For example:

To succeed in a DC 2 STR test, you roll 3d6, which in turn generate a modifier from -3 to +3, according to the table above. If you roll 14, for example, you get a +1 modifier. Add that to your STR modifier, and if the total is equal or greater than 2, you succeeded. In that example, you would need a STR of 14 or more to succeed.

As a general rule, if the DC is greater than your ability modifier, you will usually fail, because you are relying on the dice to generate a positive modifier (which only happens about 25% of the time).

Another example: the GM says that picking this lock is DC 4 (a very hard task, indeed). You have a DEX of 17, and thus a +2 modifier already. When you roll 3d6, you need to get an extra +2 to reach DC 4; thus, you need to roll rolling 16 or more. If you had no DEX modifier, the task would be impossible, because the maximum bonus you can get from the dice is +3.

I've added some adjectives (inspired by Fate RPG), but the cool thing is that you don't have too. If you have been playing basic D&D for a while, you already have your own understanding of what "STR 17" means.

With that knowledge, you can just say "it would usually take someone with STR 17 to take down this door". Well, since STR 17 has a +2 modifier (as you probably memorized already), you know the DC is 2.

Keep in mind that the dice will give you no bonus/penalty about 50% of the time, and you will succeed in a DC equal to you mod about 75% of the time. So the STR 17 girl will knock down the STR 17 door three times out of four.

That door has no chance.
Add fiddly bits to taste.

- If you have some kind of advantage, skill, tool, etc, just add +1 to the final modifier (not to the roll). This is not too dissimilar to advantage in 5E or NWP in 2E.

- Use a +1/+2+3 bonus for novice/skilled/expert. So an expert in stealth can ordinarily sneak around as if he had DEX 18, even if his DEX is only 12.

Take all this into account when calculating the modifier needed: if you need not only an expert doctor, but the most talented doctor around, you probably need a +5 or +6 to succeed.

Of course, if you roll better than needed, you use the difference to your next roll, get some kind of advantage, etc. It works both ways.

Mathematically, this works way better than most alternatives mentioned above, specially for conflicts. The STR 18 will seldom get defeated by the STR 10 guy, but the STR 16 guy has a fair shot (in direct conflicts, I would give ties to the strongest, by the way). 

It is also quite easy; the total modifier will often be equal to you unmodified modifier (pardon the pun), and you'll never need to add big numbers. In fact, the DCs will seldom be greater than 3 or 4, etc.

Interpreting the results is near automatic: rolling 14 means and above average performance, and rolling a 3 an abysmal one. When writing adventures, abbreviations come naturally: you can describe a door with "great" resistance, or mention an DEX 16 check, for example.

There are many other methods you could use, but this avoids some of the pitfalls of the first that come to mind (requiring fate dice, harder math, further tables, further subsystems, dice interpretation, etc).

The main strength of this system is familiarity (and the bell curve, if you mind this kind of stuff); if you don't think this is important, you could just ditch abilities completely, keep the mods and roll 1d6, for example.

There is some caveats, though. This doesn't take level into account (if you're not using "skill slots" or similar, you might add a fraction of your level to the roll, not the modifier, so that only the highest level thieves could fool someone smarter than themselves, for example), nor the difference between STR 13 and STR 15, for example. Still, better than most solutions I have seem.

So, what do you think? Do you know a better way to do skills in BD&D? Have you heard this idea mentioned years ago? Do you think it doesn't work at all? I'd love to hear your thoughts.

Coming up... (what would you like too read next?)
- An adaptation of this system for 5E.
- Use this exact same table for everything: reaction rolls, retainers, morale, weather, turning undead, etc.
- Could this affect combat somehow? (Hint: the answer is yes)
- Something else entirely.


  1. Sorry, I have no clue what you are saying here.

    What am I rolling. A D20? 3d6?

    And how does a Str 17 equal "roll 16 or 17" and a Str 18 equal "roll greater than 5"

    1. Thanks for the comment Steven, guess I rushed things, I will try to make it clearer. Basically, you roll 3d6 to generate abilities and 3d6 to test them. You get two modifiers: one from you ability, other from your 3d6 roll. I'm rewriting a part of it right now; I would like to hear your opinion in a couple of hours if you will.

    2. Now I understand! So your Str might give you a +2, then you roll 3d6 and look up the modifier as if it was another attribute, and add that modifir to your earlier modifier.

      Elegant, if a bit tough on the modifier zero folks.

    3. Cheers! Yeah, that's it. I really appreciate the feedback!

    4. Eric, I hope you don't mind that I am "necromancing" a rather old thread, but I like the 3d6/"Fudge" ladder idea above, and am seriously thinking about grafting onto my LotFP game. One quick question: for the specialist who purchases additional pips, which I assume translate to your "+1/+2+3 bonus for novice/skilled/expert", do the costs to purchase each +1 stay the same, i.e., one pip. And do you think there is any issue with having non-specialists have some skill points to start, and maybe a few as they progress (very few, of course).


      (I'm loving the 2d6 stuff too -- something about 3d6 curve and the Fudge adjectives, though, really appeals to me)

    5. I certainly don't mind!
      I never dug any deeper into this idea, but I'd say yes, the costs to purchase each +1 stay the same, and I wouldn't have an issue with giving a few points to non-specialists.
      In fact, I do that myself - but I also give non-fighters small bonuses to hit, etc. Or let the thief use his bonuses to increase combat - certainly wouldn't break the gem.

      Here is what I'm currently using, BTW:

    6. Excellent -- thank you for the reply.

      I am also a fan of some of your 2d6+mod variants -- which do you prefer using, 2d6 or 3d6?

      And one last question: How does 1d6+mods work? The mod changes the number to be rolled or lower?

    7. TBH, I am currently using 1d20 for PCs (and 2d6 for DMs).

      I usually prefer 2d6 over 3d6, since I can use the same table for reactions, hiring, etc.

      As for 1d6+mods, I use it like Moldvay (doors): if an ordinary character has 2-in-6 chances of success, a character with Strength 18 (+3) has 5-in-6 chances.

      In any case, I think you should use "difficulty modifiers" (maybe -3 to +3), to allow even the more skilled characters to fail in extreme tasks, and even the weakest to succeed at easy stuff.

      So: a character with Strength 18 (+3) and "expert" level athletics (+3) has 7-in-6 chances to break down a door (automatic success), but might have 4-in-6 chances to bring down a heavy gate or lift a huge boulder.

    8. Ah, cool -- thanks for the explications! Much appreciated.

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  3. This method looks a lot like Fate/Fudge, only there they use 4d6, and give modifier by die.
    So a 1 or 2 becomes -1; 3 and 4 becomes 0; and 5 and 6 becomes +1.
    This preserves the -3 to +3 range (on Fate, is -4 to +4), and no table is required.