From Final Fantasy XIV A Realm Reborn Wiki
Fell Cleave is an action unlocked by questing at level 54. It's available for Warrior.“
Delivers an attack with a potency of 590.
- Beast Gauge Cost: 50
- Action changes to Inner Chaos while under the effect of Nascent Chaos
— In-game description
- Talk to Broken Mountain - Upper La Noscea (x30, y21) - to start the Lv. 54 Quest The Bear Necessity.