Heroic Abilities are effects a player can trigger by spending Story. When you use a Heroic Ability, you make a Trigger Roll to see how powerfully you use the ability.
Any player can use any Heroic Ability, by spending story. Characters can also Master Heroic Abilities, which earns them a refund on the Story points they spend to trigger these abilities. When you use an ability that you’ve mastered, after pulling the Story point to spend, you can choose to swap out that story point for the next lower valued story point, in which case the ability still triggers as normal. If you choose to keep the original Story point, then you earn a bonus on the trigger roll.