Who is a slime demon?

[Gilladian]

In general D&D lore, is there a slime demon? a lord of fungi and oozes? In my campaign, recently, the PCs restored a winery that had been taken over by a slime cult. They slew the demon at the altar, and destroyed an important symbol of her power. Now that she's been driven back to wherever she came from, her "lord and master" is ticked at the party. They've issued him a setback in his plans, and he wants revenge. So who is he? What demon should be behind the pestering and harrassment that is going to go on? Of course, eventually they may have to do something bigger to stop the problem, but for now, I just need an idea of who/what is behind the situation so I can decide how far his reach is, etc...

 

[steeldragons]

Juiblex (or Jubilex, depending on the edition) is the demon lord of slimes.

Fungi has, at some point over the years, been granted to [the only other famed lord-level female demon aside from Lolth] Zuggtmoy.

 

[Scrivener of Doom]

In FR there is also Ghaunadaur who is an ancient deity of oozes and slimes who has largely replaced Juiblex/Jubilex in that world. He/it is also a considered a drow deity and possibly the FR equivalent of the Elder Elemental Eye and/or Tharizdun.

 

[Voadam]

Juiblex the Demon Lord of Slimes and Oozes was one of the four demon lords statted out in the 1e AD&D Monster Manual. His pathfinder stats are detailed here as Jubilex.

Pathfinder also has Cyth-V'sug a demon lord of fungus and parasites. That is from the cosmology of Paizo's world of Golarion and not official D&D cosmology.

Wikipedia has a good list of D&D Demon Lords.