The Master
An illithid of surpassing intelligence and evil, even by that race's standards. He calls himself by that name, though some sources claim his original name is "Joon Deeb." He is very tall and very thin, his originally purple skin having an oily greenish cast to it, and the tips of his tentacles and fingers are pink, possibly indicating some disease or magical affliction. He wears black robes with high collars.
He is black-hearted, infinitely cruel, ruthless, and merciless, caring only to conquer, enslave, hurt, and destroy. He is also a supra-genius, capable of concocting and carrying out incredibly elaborate and long-range plans which almost always succeed, and he never forgives and always seeks to punish and destroy those who have opposed him.
It is unknown where he came from or what he (for he identifies as male, despite mind flayers being genderless) did before he came to dwell deep under the Four Towers on the island of Nidan in the Chibouholm Isles. It was there that he, possibly with the unwitting assistance of The Legion of Llandos, succeeded in awakening the Sleeping Eye.The Master and the beholder clashed with and overpowered the Legion, but they escaped with Hachoo.
The Legion encountered the Master and the Eye again in an ancient illithid complex in the Mushroom Forest region of the Underdark and managed to slay him, though the Eye escaped with its body.
As it happens, The Master was not dead. Later he became the chief mastermind behind The Black Chorus, almost successfully orchestrating the downfall of the Legion (and succeeding in killing Camarion Llandos VII), but Ember caught him in the Bag of Capturing.
It was later discovered that he had somehow escaped from the Bag, which should not have been possible.
Sometime later, he was behind a plot to awaken a lich and conquer Sablos with an army of undead, which almost succeeded, but for the Knights of Sablos and the Legion. He was taken alive and imprisoned in the dungeon of King Oriel.
Years later he escaped again and disappeared from Jesenreth.