The Oinoloth, sometimes called the Oinodaemon, was the nominal lord of the yugoloths, maintaining their precarious position from the Wasting Tower of Khin-Oin. Oinoloths were harbingers of pestilence and the masters of wasting illness, ruling over Oinos, the diseased 1st layer of the Gray Wastes, with their power over plagues.
An Oinoloth's head resembled that of a foaming ram that had been deformed by disease. A portion of their skin had hideously sloughed off of their bodies and the wool that covered it was removed with ease. Unveiling their skin showed their boils, blisters, and pustules and their flesh was tautly strung over their bones.
Unlike the yugoloth castes, the title of Oinoloth was simply that. It was a role that was not accompanied by a truly new form but a simple transformation. Khin-Oin's rulers were always of the yugoloth race, to be more precise of the ultroloth race, and only ultroloths were known to have managed to take the title. The requirements were to vanquish the current Oinoloth and to sit on the Siege Malicious, a throne on the top of the Wasting Tower, although whether or not this required the death of the original was uncertain.
The being who became the Oinoloth was disfigured by loss of their skin, an incurable ailment so long as they held the title. But with the disfigurement came power over disease as so long as the Oinoloth was within Hades, they could create any new disease or modify existing ones as they wished whether on or away from the throne. This process was so fast that coming up with a name for the disease could easily be the most time-consuming part of creation. Once created, the Oinoloth could securely infect anybody within 300 ft (91 m) with the new disease.  Oinoloths could blight the very ground they treaded bringing disease and illness wherever they went and their claws were corrupting in their touch.
An Oinoloth also had the ability to nullify any disease they had made and cure those suffering from it, although it would permanently debilitate them by doing so. Like ultroloths their gaze was hypnotic and it charmed those that looked upon the Oinoloth.
Despite being the supposed ruler of the yugoloth race, the Oinoloth spent less time coordinating their activities and managing their plans then they did trying to keep their own position. Khin-Oin's rulers were in constant competition with each other not only over the position of the Oinoloth but on whose vision of perfection was superior. Realizing these would go nowhere, most of these competitions turned violent, with the Oinoloth simply trying to turn factions against one another in order to turn their ire away from himself. While many ambitious ultroloths gunned for the throne some cared not for becoming Oinoloth, preferring to simply manipulate those already in power.
At the end of the Silence of Lolth, Vhaeraun struck a bargain with the ultroloth Inthracis: if Inthracis successfully killed the Yor'thae candidates, Vhaeraun would kill Kexxon, the Oinoloth at the time.
- Dragon+ #21, "Six Faces of Death"
- Mike Mearls, Jeremy Crawford (May 29, 2018). Mordenkainen's Tome of Foes. Edited by Kim Mohan, Michele Carter. (Wizards of the Coast), p. 251. ISBN 978-0786966240.
- Mike Mearls, Jeremy Crawford (May 29, 2018). Mordenkainen's Tome of Foes. Edited by Kim Mohan, Michele Carter. (Wizards of the Coast), p. 257. ISBN 978-0786966240.
- Gary Gygax (August 1983). Monster Manual II 1st edition. (TSR, Inc), p. 30. ISBN 0-88038-031-4.
- Jeff Grubb, Bruce R. Cordell, David Noonan (September 2001). Manual of the Planes 3rd edition. (Wizards of the Coast), pp. 109–110. ISBN 0-7869-1850-8.
- Jeff Grubb (July 1987). Manual of the Planes 1st edition. (TSR), pp. 105–106. ISBN 0880383992.
- Colin McComb (December 1995). “Liber Malevolentiae”. In Michele Carter ed. Planes of Conflict (TSR, Inc.), pp. 52–53. ISBN 0-7869-0309-0.
- Colin McComb (September 1997). Faces of Evil: The Fiends. Edited by Ray Vallese. (Wizards of the Coast), p. 71. ISBN 0-7869-3430-1.
- Paul S. Kemp (February 2006). Resurrection (Kindle ed.). (Wizards of the Coast), locs. 84–160. ASIN B0036S49H8.
- Mike Mearls, Brian R. James, Steve Townshend (July 2010). Demonomicon. Edited by Scott Fitzgerald Gray. (Wizards of the Coast), p. 134. ISBN 978-0786954926.
- Gary Gygax (September 1986). Queen of the Spiders. (TSR, Inc.), p. 126. ISBN 978-0880383219.
- The "present day" in Swords of the Iron Legion, when Anthraxus was still in power.
- The "present day" in Faces of Evil: The Fiends, when Anthraxus had already been ousted.
- Paul S. Kemp (February 2006). Resurrection (Kindle ed.). (Wizards of the Coast), locs. 217–257. ASIN B0036S49H8.
- Mike Mearls, Brian R. James, Steve Townshend (July 2010). Demonomicon. Edited by Scott Fitzgerald Gray. (Wizards of the Coast), pp. 50, 88, 134. ISBN 978-0786954926.