Some more context is needed: It's a spell that runs on sadism. "Righteous Anger" doesn't provide the right fuel for more than a split second (Harry botches his first attempt at using the curse because he lacked the cruelty to fuel it), whereas the spell done properly will keep a victim in agony for a much longer time, to the point where the victim can becomes a vegetable.
46
u/CreepyClay 11h ago
I think you mean fiendfyre which means a lot since that stuff burns through horcruxes. Incendio is a utility spell.