The Lich King is a character from world of warcraft
Once the mortal prince Arthas Menethel, the Lich King is the lord of the Undead Scourge. Arthas led an expedition to the frozen continent of Northrend in search of the legendary sword Frostmourne; a cursed blade that consumed it's bearers soul. Infused with the disembodied spirit of the orc lich Nez'ul, Arthas betrayed his kingdom and overthrew it. He moved the capital to Northrend, where he now sits, brooding over all he has lost.