Kel'Thuzad, once a sorcerer of the Kirin Tor of Dalaran, is the chief lieutenant of the powerful Lich King. He ruled over the Eastern Plaguelands from his citadel of Naxxramas. He was voiced by Michael McConnohie. He was the final boss of the original version of Naxxramas and considered by many to be the hardest in the instance due to the stringent execution and DPS requirements.