Ner'zhul, the Lich King, knew that his time was short. Imprisoned within the Frozen Throne, he suspected that Kil'jaeden would send his agents to destroy him. The damage caused by Illidan's spell had ruptured the Frozen Throne; thus, the Lich King was losing his power daily. Desperate to save himself, he called his greatest mortal servant to his side: the death knight Prince Arthas.