Garnef

“You dare to oppose me, fool? You must not value your life. Cower before the might of the magic Imhullu: once forbidden, now unleashed!” —Gharnef's battle quote in Chapter 15 in Shadow Dragon

Gharnef is an enemy character and a dark mage from Fire Emblem: Shadow Dragon and the Blade of Light, Fire Emblem: Mystery of the Emblem, and their remakes.

Gharnef is the creator of the Imhullu spell, making him immune to attacks; however, a magician using the spell Starlight (created by his former master Gotoh) can kill him.

(Source: Fire Emblem Wikia)