Nefarian was the last boss of the entry tier of Cataclysm to be killed on normal mode, in part due to a respawn bug. The world first kill came on 13 December 2010, almost a week after the expansion's release. It was completed on 10-person mode by the Russian guild Exorsus. The world first heroic kill was on 10 January 2011 by Paragon (25 person).