Skills
Every Skill has a default Attribute/Element. A player can challenge that default with a Descriptor.
Skills Default to an Element
Every Skill is pre-assigned a default Attribute/Element - see the Default Element column in Premade Skills for the base campaign list, or set one when a custom Skill is created. Rolling a Skill normally uses its default: no argument needed, that’s just how the character does that thing.
A player can challenge the default and pair the Skill with a different Attribute instead, provided they can argue the pairing to the GM’s satisfaction. The GM has final say on whether a proposed pairing fits the situation. That argument is grounded in one of the character’s own Sub-Stat Descriptors - a specific chosen adjective the character already has - rather than an improvised justification from scratch. No Descriptor that fits, no challenge - the roll uses the default.
Challenges are re-argued every time, not banked as precedent - a challenge that worked once may not hold up in a different situation, since the justification is about the specific circumstance, not a permanent reclassification of the Skill. The default itself never changes; only the single roll in front of you does.
Training Tiers
A Skill’s training tier changes how the core roll is built:
| Tier | Name | Roll |
|---|---|---|
| 0 | Untrained | Difficulty only (no Attribute - see Untrained Rolls) |
| 1 | Novice | Attribute + Difficulty, with Disadvantage |
| 2 | Trained | Attribute + Difficulty |
| 3 | Adept | Attribute + Difficulty, with Advantage |
| 4 | Expert | Attribute + Difficulty, with Advantage, and critical success widens to a roll of 2 or 3 |
| 5 | Master | Same as Expert, plus: on a critical failure, roll again - if the second roll succeeds, it’s treated as a normal failure, not a critical failure |
Each tier is strictly better than the last. Master’s reroll only ever removes the “critical” severity from a failure (downgrading it to an ordinary failure on a second success) - it never turns a critical failure into any kind of success, and if the reroll also fails, the critical failure stands.
Advantage/Disadvantage are the standalone core mechanic: roll 3d10, keep the lowest two (Advantage) or highest two (Disadvantage).
Advancement: a character climbs the ladder one tier at a time via direct XP expenditure - no classes/levels, no fixed track. See the Advancement Reference for the exact XP cost per tier.
Everyman Skills
A short list of ordinary, baseline skills that every character starts with at no cost, reflecting the basic competence any functional adult in the setting would have. 20 Below doesn’t fix this list in the core rules - the GM decides the Everyman Skills list for their own campaign/setting, since “what any ordinary person can do” depends heavily on genre and setting. Every Everyman Skill is granted at Tier 2 (Trained) - full Attribute + Difficulty, no flat bonus or Advantage, reflecting genuine baseline competence rather than a bare exposure.
Everything else about Skills (whether there’s a fixed list beyond Everyman Skills, breadth) is still open. XP costs per tier are tracked in the Advancement Reference, not here.