When an action is uncertain and failure matters, the Game Master calls for an Ability Check.
Ability Check = d20 + relevant Ability modifier
Apply any Boons or Banes, then compare the total to the Difficulty Class. If the total equals or exceeds the DC, the action succeeds.
Do not roll when success is certain or the action is impossible. Natural 1s and natural 20s have no special effect on Ability Checks.
Choosing an Ability
The Game Master chooses the Ability that best reflects the character’s approach. The player should describe both what the character wants to accomplish and how they attempt it.
The same task may use different Abilities when approached in different ways. For example, forcing open a damaged door might use Strength, while identifying and releasing its locking mechanism might use Intelligence.
Backgrounds and Ability Checks
When a character’s Background directly applies to an Ability Check, it grants one Boon. If the task lies at the heart of that Background’s expertise, the Game Master may grant two Boons instead.
The player explains how the Background applies. The Game Master makes the final decision.
A Background may also provide knowledge, access, or experience that changes what the character can attempt or removes the need for a roll.
Assistance
A character who can meaningfully help with an Ability Check may grant one Boon to the character making the roll.
The assisting character must be able to contribute to the task. Simply being present does not provide Assistance.