The Phoenix entity became too strong to control for the merely human aspects it had acquired from Jean, but the other X-Men had no way to know what was happening and little chance of preventing a tragedy. Professor X helped Jean establish "psychic circuit breakers" in her mind, but they became less and less effective.
She was thus an easy target for the illusionist Mastermind, who needed a trophy to join the Inner Circle of the prestigious (and infamous) Hellfire Club. With the help of a psionic device created by the club's White Queen, Emma Frost, Mastermind made Jean believe that she was his 18th-century lover Lady Grey. Jean joined the club as their Black Queen, which would allow her to relish the extremes of human emotion and sensuality. When the X-Men came to her rescue, Jean's true love, Cyclops, faced Mastermind in a psychic duel and was defeated. His "death" broke Mastermind's hold over Jean's psyche--as well as any control Jean had had over the Phoenix. It brushed aside the X-Men and departed for the heavens.
Info from: marvel.wikia
I really loved when I decided to do Dark Phoenix on a minifig, it is one of my favourites because she is so powerful and nearly indestructible... any way, I can say that took my time searching on the web for the "best" idea to transform that into the usual hand made decal for her torso as well as her face... the hair was, of course, painted to give some fire effect.
And the usual question: what do you think?
By the way, I don't mind if anyone around uses my ideas, actually good to see that others are inspired by ones job, thanks! ;-) but please give the proper credit... THANKS!