The Black Magic spell Temper magically hardens the weapon of one of the caster's allies, increasing the amount of damage that the ally can do. The strengthening effect is not as powerful as that of the spell Saber, but the benefit of Temper is that Temper can be cast upon any ally rather than only upon the caster.
Temper has no actual effect on gameplay.
Temper can be cast by:
Final Fantasy Origins: Steel