The Dark Phoenix Saga
Note: The Jean in this story and Proteus is not the original Jean Grey. After a space mission in which Jean was exposed to radiation after saving the X-men and thereafter died, the original Jean was placed in a cocoon at the bed of Jamaica Bay while the Phoenix, a cosmic entity impressed with Jean’s sacrifice, created a duplicate body of Jean and became known as Phoenix-Jean and unbeknownst to the X-men that it wasn’t their Jean
Jason Wyngarde aka Mastermind gets into Jean’s head
Makes Jean think she’s living through an ancestor’s life in the 1800s
X-men are taken hostage by the Hellfire Club after psychic attacks by Emma Frost who at this time attempted to recruit Kitty Pryde into her Hellions
Hellfire Club members include Sebastian Shaw, Emma Frost, Mastermind, Donald Pierce, and Harry Leland who are all part of the Inner Circle
Leland can increase an object’s density and mass. Pierce is a cyborg
Jean becomes the Black Queen
Mastermind beats Cyclops in a psionic battle when Cyclops uses his psychic rapport to reach Jean
Killing Cyclops’ psychic form, this breaks Jean’s final mental barrier
With Jean free, the Phoenix becomes angry and becomes Dark Phoenix
Dark Phoenix beats Emma Frost in a psionic battle
Dark Phoenix flies into space where she destroys an entire solar system in the Shi’ar empire by consuming the star D’Bari
Xavier restrains Phoenix back inside Jean
Shi’ar empress Lilandra demands justice for Jean’s crimes, the penalty for which is death
X-men fight Lilandra’s Imperial Guard for Jean’s life and lose. Gladiator is the leader of the Imperial Guard and one of Marvel’s strongest characters
Jean becomes Dark Phoenix again and knows she must self-sacrifice to end the pain to herself and her friends which she does