Thief Roll

Jack from TOTGAD has an attractive house rule whereby he uses the “hear noise” d6 chance as the system for resolving all thief skills. This seems pretty reasonable to me, especially assuming that the alternative is the fixed percentile progression given in OD&D or B/X. All of the percentile skills start off rather low and slowly increase as levels are gained, with arbitrary differences between the various skills and no option to specialize in one skill over another (unlike the point buy systems of, for example, LotFP or Second Edition AD&D).

Looking at the OD&D thief (in Supplement I: Greyhawk), why does open locks start at 15% and move silently start at 20%? Do we really care about this distinction, given that all the skills start out at roughly the same level and increase at approximately the same rate? The one exception is climb walls, which starts out at 87%. But “always use hear noise” with perhaps one special case for climb walls is still far simpler than the official multiple stat percentile system, with functionally similar outcomes.

The schedule of thief hear noise improvement (from Greyhawk, page 11) is as follows. (Thanks to ODD74 for discussion about interpreting hear noise in the OD&D context.)

OD&D Thief Hear Noise
Level 1–2 3–6 7–10 11–12 13–14
Hear Noise 1-2 1-3 1-4 1-5 1-6
Effective d6 bonus +1 +2 +3 +4 +5

However, just when I was about to throw in my lot with this method, I realized that it does not allow for the variable degrees of success that I use with the old percentile system. That is, using d6, and without another roll, how do I distinguish between “no progress” and catastrophe? 16% (1 in 6) is too high of a chance for critical failure. In my current approach to thief skills, this is pretty important. Basically, if you fail your thief skill roll, but don’t roll 96 or higher, you don’t obtain your objective, but you can try again. The top 5% is the equivalent of rolling a natural 1 on an attack roll.

According to Greyhawk (page 11), pickpocket or move silently is the most favorable thief skill column, so one could just use that as a general thievery skill similarly to how Jack uses hear noise and preserve the 5% fumble chance.

11 thoughts on “Thief Roll

  1. scrivenerb

    You could re-roll on a six, if a second six comes up that’s critical failure. 1/36 chance.

    Or use close d20 equivalents for the d6 chances:
    d6 . . d20
    1 . . . 1-3
    2 . . . 1-7
    3 . . . 1-10
    4 . . . 1-13
    5 . . . 1-17
    6 . . . 1-19
    and crit fail on a 20. (Or switch it around if you want a roll of 1 to be the failure)

    1. Brendan Post author

      Yeah, but saying “just use hear noise” is so much easier! This is totally reasonable though, and works if you don’t mind another house rule.

  2. Ramanan

    I was going to suggest switching to a d20 as well. You could give thieves an extra saving throw that improves at the rate you need. A 20 is always a critical failure.

    1. Brendan Post author

      I actually do have a d20 solution to this that I prefer (which is part of a separate project), though again you run into the “new system friction” downside. I was trying to work using OD&D numbers here.

  3. guest

    That would nerf high level thieves in BX/LL. Basically, anyone above level 8 this is actually interfering with instead of helping.

    Also it means thief skills don’t change for several levels at a time.

    1. Brendan Post author


      I assume you are referring to Jack’s d6 method? It’s true that the number improves less frequently, but it also starts higher for all skills (2 in 6 is over 30%) and jumps in bigger steps. I don’t necessarily see this as a problem; it is reminiscent of the B/X attack matrix (which also only improves every few levels).

      If the bigger jumps are a concern though, using one percentile number for all skills would work, right?

      I don’t see how it nerfs high level B/X thieves. Could you expand on that?

  4. John Laviolette

    Delving Deeper’s solution was to use 1-4 on a d6 roll as the chance of success for any thief skill at any level, which is a little like your solution, although it eliminates a feeling of advancement (except for damage from a surprise attack, which still increases.) You can kind of get that feeling back by giving a thief a +1 bonus if their level is higher than the target’s level (or dungeon level, for picking locks.)

    My solution was closer to yours, although I phrased it as being based on surprise instead of Hear Noise. My thieves are more likely to surprise and less likely to be be surprised: add hit dice (or half level, round up) to the chance of success.

    I don’t use a catastrophe system for thief skills, myself. I figure catastrophes should be based more on what the thief is doing, rather than a die roll. For example, if picking the pockets of a villain, failure means discovery if the villain’s Wisdom is higher than the thief’s Dexterity. But I could imagine a couple situations where I’d simply make a second roll or a saving throw to avoid something going horribly wrong.

    1. Brendan Post author


      I agree that “catastrophes” should be situational. The word is probably too strong, but none of the other options are much better (fumble, critical failure, over-failure).

      Adding a second roll/saving throw does address the problem (in fact, unstated above, for climb walls I would probably do 5 in 6 followed by a saving throw if the thief roll is missed; that pretty closely mimics the original percentage advancement).

      This is also a bit like Ynas’s solution (linked below) to roll a second d6 to determine if a catastrophe occurs. It also improves with level. Or scrivenerb’s constant 1 in 36 chance of fumble (also requiring a second roll, described in the first comment above).

  5. Joshua Lyle

    I’d consider adapting the LotFP rule that a 6-in-6 chance fails on boxcars, and have that be the critical failure result


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