Though his powers were drained by the Lich King's weakness, Arthas had been involved in a civil war in Lordaeron. Half of the standing undead forces, led by the banshee Sylvanas Windrunner, staged a coup for control over the undead empire. Arthas, called by the Lich King, was forced to leave the Scourge in the hands of his lieutenant, Kel'Thuzad, as the war escalated throughout the Plaguelands.