Kazzak was one of the demon lords that Archimonde brought with him during the attack on Azeroth. At the end of the Third War, Archimonde was killed, and Kazzak was forced to flee to the Blasted Lands. Lord Kazzak was introduced into World of Warcraft in patch 1.3 as a boss located in the Blasted Lands sub-zone, the Tainted Scar. When the game's first expansion, The Burning Crusade, was released, Kazzak apparently got a promotion to Doom Lord after reopening the Dark Portal, and relocated to the Outlands.
When the demonic Burning Legion invaded the world of Azeroth for the 2nd time, Archimonde, field commander of the Legion, brought with him his top lieutenants. One among them was Lord Kazzak. During the battle at Mount Hyjal, Archimonde and most of his lackeys were killed. The only survivors of this battle were Kazzak and Pit Lord Azgalor. Azgalor fled Azeroth soon after, leaving Kazzak in control of the remaining Legion forces on Azeroth. Kazzak made his main base of operations in the region known as the Blasted Lands. Unfortunately, Kazzak was completely cut off from other Legion members on Azeroth. Even if he could, they would most likely avoid him in fear of his great power. Eventually, he found an ancient relic that would allow him to accomplish his goal to reopen the Dark Portal. He put the relic to use, and opened the portal that led to the shattered world of Draenor, now known as the Outlands.
In The Outlands
When he opened the Dark Portal, he left his minion, Highlord Kruul, in charge of the Legion on Azeroth. Kazzak was promoted to Doom Lord after opening the portal, and set up his new main base of operations on a mountain known as the Throne of Kil'jaeden. He deployed his minions, Arazzius and Vorakem, to lead the Legion forces on the ground. During the war against Illidan Stormrage, the heroes of Azeroth learned of Kazzak's location, and mounted an assault on the Throne of Kil'jaeden. Kazzak was heavily guarded by the Legion, but his guards were slain and Kazzak and the heroes battled. Kazzak was defeated, but his fate remains unknown as there has been no mention weather he was killed or merely defeated.