Socothbenoth the Persuader is the Abyssal+lord of incest and other sexual taboos and perversions. His sister Nocticula is also his lover. He lusts after the power of Graz'zt, and so has allied with Malcanthet against him.
His Realm, Goranthis, is catalogued as the 597th Layer of the Abyss. It's an infinite pleasure palace that includes a sculpture garden called the Saturnalia and Socothbenoth's personal abode, the Palace of Quivering Flesh. The River Styx impinges on this domain. Socothbenoth is served by advanced Shadow demons known as the Shadows of Socothbenoth, who whisper and cajole those Socothbenoth favors into joining their master's service.
Fiendish Codex I: Hordes of the Abyss, page 156
Dragon #353, page 27 - "The Demonomicon of Iggwilv - Malcanthet"
Dungeon #147 - "Into the Maw," by Robert J. Schwalb
Dragon #358 - "The River Styx" by F. Wesley Schneider
The Book of Fiends: Armies of the Abyss (d20 product from Green Ronin)