In Dance of Demons he allies with Iuz and alternates attacks Graz'zt on the opposite side with the aid of troops from Infestix. He leads Mandrilagon, a devil legion, a dreggal division, and various daemons and cacodaemons. Twenty Ahazu-demons serve as his officers and guard. He also has sixty battle-gongs. He is loaned a Theorpart by Infestix (the Initiator). He goes home when Gord slays Infestix. When most demons ally, he leads the water demons and takes Graz'zt's right. He owns the Venom Fountain. (ref. medieval demon mistakenly thought to belong to an ancient mythology. His name was a corruption of Demiourgos from Plato's Timaeus, which found its way into the works of Boccacchio, Spenser & Milton. see here). See also Monster Manual I
Judging from S4, The Lost Caverns of Tsojcanth, Monster Manual II, and the 1983 World of Greyhawk boxed set, Graz'zt was captured by Iggwilv through her demonological practices around 460-470 CY, wresting him from the middle of a crucial battle. Either during his imprisonment or immediately following his accidental release he sired Iuz upon her. To what degree this union was consentual is unknown, but the battle that followed his release resulted in his being confined to his home plane for several decades, perhaps a century.
As of the beginning of Artifact of Evil he has made use of his new freedom and controls three layers of the Abyss. He has granted Iggwilv amnesty from any vendeta he might carry, so that she might aid Iuz; Yeenoghu allies with him. His agents, along with Iuz, seek the two remaining theorparts. By the end of Artifact of Evil his coalition controls 66 layers of the Abyss. They open a gate to Oerth. Hill, Mountain, and Frost Giants roam from the Howling Hills South and drive out the Hierarch's hobgoblins and orcs to the Felreev and the Steppes. He conquered Prince Ariax.
At the beginning of Sea of Death, he has extended his personal realm to eight planes. By the time of his meeting with Iuz's faction and Iggwilv, he controls twelve layers. He receives the Unbinder when it is recovered.
Towards the beginning of Come Endless Darkness, 66 greater and lesser demon lords bow to him and through them he controls 333 planes. His personal territory is called Greater Mezafgraduun. Baphomet has joined him and they have retaken the cataboligne demon home plane. He goes "north" with Pavlag, Nergal, Ogrijek, and Kostctchie to meet the attackers on Zuggtmoy's side. He uses thousands of nabassu scouts. He and Nergal know of Leda's alignment, but keep her because of Vuron. He can use the Eye of Deception or the Theorpart to grow to 300 feet tall, and to alter reality (making no flight possible from the battle on Ojukalzogadit). He uses the two artifacts to turn the tide of battle for him. He learns that whom he thought was Eclavdra is Leda after she helps Gord fight Infestix. He has 30,000 elite troops who surround Gord, Gellor and Leda from the front and two flanks. He strides to the front. He leads the united force of demons verses Gord. They total 50 noble demons, 300 petty lords, and millions of minor demons. They gather in Iyondagur where Entropy meets them. When Tharizdun takes over, he makes his stand with Elazalag and the rest of the Abat-dolor on Ojukatazogadit.
He is the Master of The Roving Hordes, controling two-thirds of Graz'zt's forces. He tollerates no sycophants. A master strategist, he leads forces through Tartarus against Hades's gates. He goes to the Cyanic Fens with Leda as Eclavdra, Yeenoghu, and twelve other minor demon lords to meet Iuz and other attackers.
In Dance of Demons, he waits for battle on a flat plane, controlling a force of all the "Type" demons save Type 5, also including dretch and rutterkin. He has previously sacked Mandrilagon's palace and kidnapped Demogorgon's harem. He enters personal combat with Demogorgon while carrying his crystal spear. He can use the Theorpart to heal and to promote demons. He sends Leda as a messenger to Graz'zt, hoping to destroy her influence. He is slain by Leda.
He can, through his finger, cast a putrescent green ray, which, upon striking its victim causes their flesh to bubble and their body to melt. He is not shy about using this technique on those who have failed him. He likes to geas those who have insulted him with lethal disease effects. He can cause instant rot in the living, this kills by the touch. He can regenerate lost limbs. He is conceited, plotting, and smug. He is master of daemons and ruler of Hades. He has many attendants, including "the diseased ones", oinodaemon types. He uses dreggal scouts and has the messy habit of killing his messengers.
He sends part of his essence with Sckculintig to spy on her dealings. He is the primary advocate for the return of Tharizdun. He comes to the battle on Ojukalazogadit with concealed aid by theorpart. He observed the contest between Gord's party and Gravestone. When Entropy makes his move in the beginning of Dance of the Demons, even he is in trouble. He gives aid to Iuz and Demogorgon to topple Graz'zt. He loans Demogorgon the theorpart (the Initiator), but he has built in a harmonic retrieval device. Once Vuron is lured into personal combat with Demogorgon, he sends in the eight oinodaemons and a daemon horde. Gord and Gellor confuse him with the Banner of Basiliv. His material form is slain by Gord, banishing him to Hades, and loosing him the Initiator. He lost his hand to Gord, but he can regenerate it.