Real Name: UnknownMastermind is most noted for using a mind-tap device to convince Phoenix II that she had loved him in a previous life, thereby seducing her into becoming the Hellfire Club's Black Queen, a move which precipitated her transformation into Dark Phoenix. When she broke free of Mastermind's control, Phoenix expanded his consciousness to god-like proportions and he nearly went insane for a time. He returned to disrupt Wolverine's marriage to Mariko Yashida and then to convince the X-Men that Madelyne Pryor was Dark Phoenix reborn in an attempt to ruin her wedding to Cyclops by having the X-Men kill her. This taking of an innocent's life would also have destroyed the X-Men as individuals and as a team. Due to his prior experience with Mastermind, Cyclops was able to discern his involvement and work through the illusions to defeat the villain. Mastermind apparently was then transferred to the Muir Island facility.
Shortly after the formation of Excalibur, Mastermind lured Captain Britain to his cell and switched places with him. He used Cap's form for a while, and though his teammates noticed a surly change in personality, and Widget and Lockheed reacted to him with unease, no one detected his presence. Finally, Mastermind made his move on Phoenix III, posing as her dead love Franklin Richards (from "Days of Future Past") and maneuvering her into mind-linking with him. Through the mind-link, Mastermind was once again in touch with the god-like power the original Phoenix had exposed him to. Fortunately, Nightcrawler deduced Mastermind's involvement and snapped Rachel out of his illusion. Rachel then called on the full power of the Phoenix, ripping it away from Mastermind and leaving him nearly a vegetable. He was returned to Muir Island.
Over time, Mastermind's mind healed itself somewhat, but he then contracted the Legacy Virus. Before he died, he wanted to apologize to Phoenix IV for what he did to "her" while he was with the Hellfire Club. Phoenix, Iceman, and Bishop came to Muir, and Mastermind linked with them, putting them in a fantasy scenario in his mind. He intended to give them the gift of their realized dreams, but his powers were so out-of-control from the Virus that they were trapped. His last act was to shove Jean out of his mind, so that she wouldn't die with him.
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