When your HP goes below 25%, you gain the effect of Provoke L10 on yourself. That means +32% ATK and -60% VIT DEF. The effect lasts until the character returns to more than 25% HP. The skill can be set to activate or not. The skill will even function after it has drained all your SP.

Empowered by rage, character enters condition that is equivalent to Level 10 Provoke status when HP is reduced to less than 25% of Max HP.
Provoked status lasts until character HP is restored to more than 25% of Max HP or if Provoke effect is nullified.