Frostmourne was a runeblade kept away from the Frozen Throne by Ner'zhul, the Lich King, in the hope that Arthas Menethil, his unsuspecting future master, would discover the blade on the continent of Northrend. Frostmourne was wielded by Arthas Menethil, the new Lich King, until the blade was destroyed during Arthas' defeat at Icecrown Citadel.