Kel'Thuzad was originally a mage of the Kirin Tor, but he was later enslaved by the Lich King. He founded the Cult of the Damned, a group that worshipped the Lich King. He became one of the Lich King's most important servants, and he was responsible for unleashing the undeath plague in Lordaeron. Kel'Thuzad was slain by Arthas, who then later resurrected by him as a lich, so he could summon Archimonde the Defiler. Kel'Thuzad was tasked by the Lich King with commanding the Scourge of Lordaeron from his necropolis, Naxxramas.