The Dark Phoenix Saga, written by Chris Claremont and John Byrne, is regarded as one of the greatestif not the greatestX-Men stories of all time. After nearly dying, Jean Grey gained the cosmic power of the Phoenix Force. The Hellfire Club wants the power of the Phoenix for their own goals, and one of their members, Mastermind, begins manipulating Jean with the aid of Emma Frost. This manipulation leads to Jeans corruption. The Phoenix breaks through the barriers on her power and renames herself Dark Phoenix. Desiring more power, the Dark Phoenix drains the energy of a star, which wipes out the entire population of the DBari solar system. This leads the Shiar Empire, as well as the Kree and the Skrull, to declare that the Dark Phoenix poses a threat to the universe and must be killed. The X-Men intervene on Jeans behalf and Professor X challenges Lilandra to a duel for the fate of the Phoenix. In the end, Jean ultimately sacrifices her own life for the good of the universe. The original ending would have featured Jean being de-powered, but editor in chief Jim Shooter felt Jeans survival presented a moral problem for the X-Men after she killed billions. Kurt Busiek, who would later go on to become a Marvel writer himself, came up with a solution to this problem. His idea was that the real Jean Grey was still alive and kept in a cocoon at the bottom of Jamaica Bay. The Phoenix had simply assumed Jeans form and memories, but was a separate entity. This idea made the rounds among writers and Shooter accepted it, green-lighting X-Factor, which reunited the five original X-Men. Busiek was credited and paid for the idea. Some, including Claremont, werent satisfied with the retcon, feeling that it cheapened Jeans sacrifice. Others were pleased to have Jean return to the world of the living.
Percival Constantine is the author of several novels and short stories, including the Vanguard superhero series, and regularly writes and comments on movies, comics, and other pop culture. More information can be found at his website, PercivalConstantine.com