Ilsidahur, the Howling King, resembles a gigantic ape with a long prehensile tail and huge bronze ram-like horns. He is lord of the Bar-lgura demons. His lieutenants are Nalfeshnee.
Ilsidahur is ruler of a layer of the Abyss called the Guttering Grove (catalogued as the 90th). There he guards the landward approach to the Gaping Maw of Demogorgon. He and Demogorgon are allies, and together they invaded Arborea and captured Gwynharwyf, though the latter escaped while they were bickering with one another.
He cannot manifest on the Prime Material Plane because of his banishment by a wizard called Tselibor.
Sources:
Fiendish Codex I: Hordes of the Abyss, pages 139 and 155; "The Shrine of Ilsidahur" from Dungeon #10; "The Demonicon of Iggwilv" from Dragon #357, page 25
- 947 reads