A darkness who was ancient even in the early days of the world's existence, Mercurial is the embodiment of rage and vengeance in the souls of those long dead. Sharing many similarities with ghasts and evil spirits, it haunts and stalks the living with restless fervor, unhindered by physical boundaries, and can harness the very life-energies of its dying allies into destructive force against the enemies of the Scourge, all for the glory of the Frozen Throne.