Plague of Undeath

The Plague of Undeath (blight or simply the Plague) is a magical affliction first conjured by Ner'zhul, the Lich King (under the direction of the demon lord Kil'jaeden), from his icy prison within the Frozen Throne in Northrend in order to create the Scourge. The Scourge was intended to be a vanguard for the Burning Legion, Ner'zhul's captors, during their attack on Azeroth. Wowpedia - 
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