Faction: The Scourge is the Lich King’s undead army, which encompasses the majority of undead on the world of Azeroth.
Event: The Scourge of Lordaeron was a military campaign in which Lich King Ner’zhul brought the Northern continent Eastern Kingdoms to its knees and turned its human populations into undead servants. These humans were later freed by Sylvanas and joined the Horde, becoming the playable undead faction.