"The huge product created by the fusion of countless brains, covering the rolling tentacles, boiling and growing like embers behind the fire, shining with the bright light of spiritual power."
The Mastermind is the leader of the mind flayer city. It can telepathically contact all the mind flayers in the city. For the mind flayers, the Mastermind is the mother, speaker, judge, arbiter, ruler and library.
The mutated Perfect Mind Flayer mastermind is still a powerful psion, gaining unprecedented power after losing his right to rule the city.