The Fall of the Scourge officially began with the Battle for Light's Hope Chapel, when the mightiest of the Lich King's champions, the Death Knights of Acherus, defected from Arthas' control. Although fighting in the Plaguelands had been raging on and off for several years, the war for Northrend officially began when the dread Citadel of Acherus arrived above the Scarlet Crusade's last stronghold. Adventurers in service to the Argent Dawn had fought with the undead many times, but, even with all of their planning, all of their skill and hard work, nothing could prepare them for the force of the assault that the Lich King brought to bear against them.