When the Burning Legion began its second invasion of Azeroth, Lord Kazzak participated it, being summoned by Kel'Thuzad near Dalaran, coming right after Mannoroth. His most fearsome lieutenant was Razelikh the Defiler. Following the defeat of the Burning Legion at the end of the Third War, the remaining enemy forces, led by the colossal demon Lord Kazzak, pulled back to the Blasted Lands. He tasked Razelikh to secure the land.
In the year 25, Kazzak was located in the Tainted Scar, terrorizing the adventurers of the Horde and Alliance.