Doom Knight lore.

Once a hero whose deeds were recorded as legendary feats, this mighty warrior fell in battle with the Doom Lord and was forcefully revived as a soulless creature filled only with rage. In an ironic twist of fate, the former champion is now a loyal servant of his nemesis, fulfilling the Doom Lord's every whim with utmost devotion, and earns the new title of Doom Knight. Boasting an incredible brutish strength matched by none, the Doom Knight tears through enemy ranks with unstoppable momentum, pulverizing whatever blocking his path. A single attack of this creature can shake the earth itself and force entire armies to flee in terror. A beast that doesn't feel pity, or remorse, or fear; the Doom Knight awaits those foolish enough to meet him in single combat and face what can only be described as nightmare incarnate.