Ioulaum

Ioulaum was a great archwizard of Netheril, a beloved champion of his people and the inventor of both the mythallar and the flying enclaves of his empire. When Ioulaum abandoned Netheril to escape the life drain dweomers of the phaerimm, panic spread at the news of his disappearance, leading to Karsus casting his spell Karsus's Avatar. Since the fall of Netheril, Ioulaum has survived as an Elder brain (the central brain of an illithid community) lich.

Ioulaum is believed to have been responsible for the creation of the first Alhoon from his illithid students (he used an arcane ritual to fuse the brains of those students into a elder brain that he than took full control of, destroying their individual wills in the process).

Today he is known as Oracle of Ellyn'taal (and is not suspected to be Iolaum), and the few who ventured into his halls gained pieces of arcane knowledge dating back to formation of Netheril, but at a terible price - voluntary losing portions of the applicants' sanity, or pieces of the applicants' arcane knowledge.