The Lich King

The Lich King is the master and lord of the Scourge, which he rules telepathically from the Frozen Throne atop the Icecrown Glacier. Kil'jaeden created the Lich King ages ago from the spirit of the orc shaman Ner'zhul to raise an undead army to conquer Azeroth for the Burning Legion. Initially trapped within the Frozen Throne with Frostmourne, the Lich King eventually betrayed Kil'jaeden and merged with the human Arthas Menethil. When Frostmourne was destroyed and Arthas perished, Bolvar Fordragon became the new Lich King, imprisoning the master of the Scourge within the Frozen Throne once more in order to protect the world from future threats. Following the events of Battle for Azeroth, Sylvannas Windrunner traveled to Icecrown to fight Bolvar, eventually tearing the helm from his head. She then destroyed the crown, and presumably, the lich king along with it. The Lich King was sent to Azeroth through the Great Dark Beyond, landing in Northrend where the ice that encased him formed into the shape of a throne, The Frozen Throne. Here, he would begin the formation of the Undead Scourge and in the process weaken the world in preparation for the Burning Legion. This new army would not fall victim to the petty infighting that had caused the orcs to fail in conquering Azeroth earlier. Sent to watch over him were the dreadlords, led by Tichondrius himself. Within the Frozen Throne, the Lich King experimented with his psychic powers and enslaved the local indigenous life forms. The plague of undeath that came from the Frozen Throne transformed each of them into his undead servants. Thus, using his psychic and necromantic powers, he was able to conquer much of Northrend. As he devoured more and more souls, he only grew in power as the individual undead under his control gave him "much needed nourishment". Thus, his powers began growing at an exponential rate; a fact that the dreadlords were well aware of and kept a good eye on him.