George Pollard

Roll-under Skills

1 min read

Roll under your appropriate skill to do the thing. Much of the time the dice will match the generation method for the skills, but this is not always the case (e.g. Cairn uses d20 vs a 3d6 skill).

2d6

Used by games in the Advanced Fighting Fantasy (1989) family, like Troika! (2019). Roll under Skill attribute + trained skill modifier.

d100

Used by Basic Roleplaying 2e (1980), Call of Cthulhu (1981), Warhammer Fantasy Roleplay (1986).

3d6

Used by GURPS and derived systems..

d20

Hinted at by the X D&D (1981) rules (B60):

"There's always a chance." The DM may want to base a character's chance of doing something on his or her ability scores (Strength, Dexterity, and so forth). To perform a difficult task (such as climbing up a rope or thinking of a forgotten clue), the player should roll the ability score or less on 1d20. The DM may give a bonus or penalty to the roll, depending on the difficulty of the action (-4 for a simple task to +4 for a difficult one). A roll of 1 should always succeed, and a roll of 20 should always fail.

Skills with roll-under appear as part of RC D&D (and maybe earlier editions as well?)

Used by Maze Rats 0.1 (2015), Cairn 1e (2020), and The Black Hack v1.2 (2016). For these games this means initially (d20 < 3d6) you have a 47.5% chance of success.

Whitehack 3e (2021) uses less-than or equal to the target, which gives a (d20 ≤ 3d6) 52.5% chance of success.

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