At the climax of the war for Northrend, the Lich King was defeated by Highlord Tirion Fordring and his champions.
Initially trapped within the Frozen Throne with Frostmourne, the Lich King eventually betrayed Kil'jaeden and merged with the human Arthas Menethil. Kil'jaeden the Deceiver created the Lich King from the spirit of the orc shaman Ner'zhul while Zovaal the Jailer forced the Runecarver (imprisoned Primus) who was forced against his will to do so by the Jailer to create both Frostmourne and Helm of Domination The Jailer intended to use the blade and the Helm to establish his influence on Azeroth, thereby allowing him to claim his 'final prize', a secret that the First Ones sought to hide to raise an undead army to weaken Azeroth in preperation of the Burning Legion's invasion.
The Lich King is the master and lord of the Scourge, which he rules telepathically from Icecrown Glacier atop the Frozen Throne.
