Demon Light (不浄の魔光 Fujō no makō, lit. Corrupted Demonic Light) is exclusively used by Fomortiis in Fire Emblem: The Sacred Stones. When cast, masses of corrupted light will swirl into the depths of Fomortiis' eyes, causing them to glow with a sinister aura. As this wicked glow dissipates, the selected enemy target will be inundated by a concentration of twisted, befouled energies, sustaining copious amounts of damage in the process. Within the game's data, this weapon is described as "a malefic flash that destroys everything it touches".
Out of the three weapons that Fomortiis possesses, Demon Light is considered to be his weapon of choice, as he most commonly uses it when engaging the player's army in battle.