Pazuzu was the winged demon prince of the Infernal Legions durion the Chaos Wars at Nishnatoba. Khalas, the Wanderer, of the Triumvirate, discovered his existence, and appeared during the great battle of the Gods to route the Elder Gods. When the Triumvirate's traitorous plans failed, the Tribunal banished Pazuzu to the Chaos Plane, where he remained for some time, until an uprising within the plane saw him weakened and cast out.
Shortly after his arrival in the Chaos Plane, Pazuzu, Slith, and their Inferno Legions expressed alarm as their environment received the brunt of the chaos dispersed by Ayar (see: The Mythos of Achaea) and began to warp and mutate, creating chaos thralls - among them, Jy'Barrak Golgotha. Eventually, Pazuzu's arrogance and oversight let Golgotha stage a successful coup d'état, swaying even Danaeus, Pazuzu's chief advisor, to his cause. By Golgotha's command, Pazuzu, Slith, and Slith's chief advisor Zsarachnor were exiled to the Prime Material Plane.
While on the Chaos Plane, Pazuzu was summoned by the arcane rituals of the Tsol'teth lords Agith'maal, Terrin'ukia, and Gattan'lier. The demon prince appeared only briefly, much to the Tsol'teth lords' chagrin, and uttered only one word: "Seleucar," before vanishing once more into the ether.
Pazuzu was not heard from again upon the material plane until the end of Kasmarkin, the mighty troll empire. He conspired with the Mad Emperor, Emperor Rakmarkha III. The Emperor learned of the demon lord through his dabblings in the occult and communications with the Unborn Goddess, (later discovered to be Eris.)
Rakmarkha knew Pazuzu by another name, and together they planned to use Kasmarkin as a gathering point for the energies of chaos. His plan failed when Senator Schlastan, as well as several other members of the senate, such as Alcibiades, learned that he was Pazuzu, and used the knowledge of his true identity to defeat him. Pazuzu was imprisoned within a crystal by Schlastan. The Mad Emperor and his followers attempted to sacrifice themselves to free Pazuzu, but only succeeded in sending Kasmarkin into the depths of the Mannaseh Swamp.
No more was heard of Pazuzu until Shakti and Silverstorm raised Kasmarkin during the Modern Age. Pazuzu's cage had been revealed. This opened the opportunity for Xerimor to go forth much later and raise the demon lord, heeding his request for revenge and summoning an army to raid the Chaos Plane, bringing forth Danaeus to be imprisoned by the will of Pazuzu. Justice for this act was swift, and Jy'Barrak Golgotha quickly enacted retribution by freeing Danaeus and putting Xerimor in his place.
Pazuzu was unable to permanently escape his imprisonment through all of this, though it is whispered that he made be freed to this day, were one to raise the lost city of Kasmarkin.