The System

When calling for an important challenge that would normally be a single roll, instead have the player make three rolls. The first is at normal difficulty, the second is at a -5 penalty, and the third is at a -10 penalty. Count each successful roll for a results range of 0-3*, and use those for the result rather than a single roll’s margin of success.

* or 0-6, if you’re having critical results count double

The Design Reasoning

I sort of arbitrarily generated this dice mechanic for my Beyond the Wall game and have been using it ever since because it worked out so well. The initial inspiration for it was simply that the party’s extremely charismatic fighter was haggling with a succession of highly-skilled merchants. BtW is a roll-under system, so the PC was trying to roll under 21 (i.e., would be automatic except 20s always fail) and the merchants were trying to make targets in the high teens. Essentially, it was very likely that they’d both just succeed, and if I applied a penalty to a single roll the swing of the dice would still likely drown out the difference in skill.

I tend to find this to be a huge problem with contested challenges in D20 in general: when there are two rolls and you’re just going for a simple highest result, there’s a lot of space in the 400 results for the lower-skilled individual to win. There’s nothing quite like your master thief regularly failing stealth rolls against unskilled opposition because you rolled low and they rolled high.

So the system is primarily for contested checks, but also serves as a decent system for knowledge checks and other rolls where you’d normally expect the results to be presented in a tiered table (e.g., “If she rolls 10, she learns… If she rolls 15, she learns…”). Similar to contests, those types of checks can result in annoyance when highly skilled characters roll low. The math on the tiers are weird anyway: your skill total impacts the chance of learning the minimum result, but each higher result is just a 25% chance because of the flat results on a d20.

Ultimately, this system is doing two things:

  • It’s adding in some normalization and curving so the swinginess of a d20 doesn’t have an outsized effect on an important challenge. Three rolls will have a much higher chance of providing a more average spread of results, so a single good or bad roll at the wrong moment doesn’t overwhelm the character’s skill.
  • It’s putting in some raises to pull apart the difference between highly skilled and exceptional. It’s particularly meaningful in a roll-under system like BtW, where scores above 19 only matter if you’re suffering a penalty. But it can also matter to highly-skilled characters in a roll-over system, where a really high bonus isn’t that different from a decent bonus at low DCs.