After the Cataclysm
According to the Demonomicon, he is a schemer, who was once a devil and advisor to Asmodeus. In that role, he was to infiltrate the Abyss as part of the Blood War. He succeeded and some have speculated that even in his position as demon prince he works for or with Asmodeus. Graz’zt is perhaps most well-known for his long-standing battles against both Orcus (d, for now) and Demogorgon. He has obsidian skin, six small horns, and six fingers. There is no other creature quite like Graz’zt.
He frequently allied with Eclavdra before her demise. Iggwilv has been his consort; it was through this relationship that she got most of her information for the Demonomicon. According to her, he once, long ago, petitioned Dagon, though the results of that petition are unclear. His daughter Pietra was once to assassinate Mjoll and Miressë – they let her live, only to team up with her later, when she stole Orret’s body from under their noses.
Graz’zt gave Zuggtmoy, a plague demon which infected New Ilion, the names of Mjoll and Miressë because he wanted them dead. It seemed possible to Zuggtmoy that he could be serving another, though she had no concrete evidence or information.
When Iggwilv joined the tenuous alliance of our heroes, Shar’eyl, and Dispater, she told them that Graz’zt wanted to move to take Avernus, to trap Demogorgon in Dis, and be proclaimed an Archduke of Hell. (During this time, Graz’zt’s lover Inanna was working for the Cerulean Sign. See her page for more information.)
From Shar’eyl, Miressë learned that Graz’zt stole something from Lolth, something like a phylactery. Graz’zt later incapacitated our heroes by whispering, taking advantage of their already-present madness. He was only concerned with recovering Inanna. Shar’eyl, who betrayed our heroes in aiding him, was possibly what had kept them alive.