Bonus Dice/Penalty Dice & Not Roll Under ?

You'd think bonus and penalty dice would be used a lot more in "roll under" rpgs?
It seems more intuitive, to me.
Am I full of shit?

I guess if you're not doing math, like trying to hit a target difficulty number, it might be fine? Dice pools is what I guess I'm talking about.


  • To me it feels like they can really easily throw the math off, and for most TN-based systems it's going to be easier/more intuitive to adjust the TN than it is to eyeball new dice probability curves on the fly.
    But if your system is something like "roll 2d6 under a target number," then "roll Xd6 and total the two highest/two lowest" could probably work.
  • Roll under rpgs usually consisted on rolling under a stat or skill, with a penalty expressed as a negative number that got subtracted from your stat or skill, not your roll.

    Like in GURPS, hitting someone in the arm with an arrow is something like -4 to your skill.
  • I do think bonus/penalty dice are more intuitive, but it can change the probability curve drastically
  • edited February 12
    I'm pretty sure I've seen some old D&D rules where ability checks were made like this:

    * If it's a difficult task, roll 4d6 (and hope to roll under your ability score).

    * If it's a standard task, roll 3d6.

    * If it's an easy task, roll 2d6.

    Like any other game design, there are going to be quirks and advantages/disadvantages to any approach. I suspect this one isn't used often due to its granularity (in my example rule, you have three different levels of difficulty, but with linear modifiers you can distinguish between a -1, a -5, a +3, a +2, and so on), as well as other issues or quirks.

    I tend to prefer to design rules which operate like this, though. Picking up different dice, and having that do the math for you, is something I favour in design. It's a purely aesthetic choice, though; I don't see any objective benefit to choosing one way over another.
  • I suppose that the main drawback is that the most common roll-under systems are GURPS (3d6) and BRP (1d100). In GURPS you are already rolling 3d6 so adding more dice will complicate the logistics (more dice to be carried) and the operations (select the 3 highest/lowest D6s from a roll of (3+n)D6). In BRP it is even worse since each dice is, indeed, a pair of dice, so you would need to use pairs of different colors or roll them once and again, taking note of the highest/lowest result rolled so far...

    This being, said, I don't think there is something inherently wrong with the roll-under + bonus/penalty dice combination, it is just that the current state-of-the-art in roll-under systems do not match well with the bonus/penalty dice mechanic.

    Indeed, since I hate arbitrary sum of bonus and arbitrary target numbers in RPGs, I would definitely want to see more RPGs using this combination: roll-under + bonus/penalty dice.

    Even if the resulting probability curve is not as "precise" as in other systems because "precision" in this context is completely overrated!
  • For example, The Black Hack is a very straightforward "roll under" system. You have six stats (Strength, Dexterity, etc.) rated 3-18 and you roll a d20 under the stat to succeed at a task.

    It's complicated by Advantage/Disadvantage (roll 2d20 and keep only the best/worst result) and big monsters (their HD is a penalty to your roll).

    The 1-20 curve is wide enough that it could tolerate +1d4 or even +1d6 as a penalty. I'd be loathe to reach for a +1d8 penalty, preferring +2d4 for the less swingy range that centers to the midpoint around +5, which is a fairly large penalty in a d20 game.

    Still, yeah, penalty dice seems like a great thing. Easy to deal with. Adding small numbers is not that difficult.
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