From Final Fantasy XIV A Realm Reborn Wiki
Kassatsu is an action unlocked by questing at level 50. It's available for Ninja.“
Allows the execution of a single ninjutsu without consumption of mudra charges.
- Additional Effect: Increases damage for the next ninjutsu action by 30%
- Duration: 15s
- Recast timer of mudra is not affected by the execution of this action.
— In-game description