When Jean Grey erupts in golden light at the end of the film, most people's first instinct is to think of Captain Marvel absorbing the Tesseract. But if you've flipped through the source comics, you'll find that X-Men: Dark Phoenix quietly left out a much darker twist: the blacked-out Jean Grey on screen isn't actually Jean Grey at all in the comic-book universe.
Here's how the original story goes: Jean is kidnapped by Sentinels aboard a space station. When the X-Men go to rescue her, they run into a real solar flare, and Jean takes it on alone to protect her teammates. Dying, she draws the ancient Phoenix Force to her. The Phoenix Force strikes a bargain—it reads Jean's consciousness, copies her appearance, and hides the real Jean in a cocoon at the bottom of New York harbor to heal. From then on, the person who goes on missions with the X-Men and whom her teammates believe to be Jean is actually the Phoenix Force itself. It maintains the "Jean" persona while carrying out its cosmic balancing duties, until a villain's illusions crack its mind open and its true nature is exposed, turning it into Dark Phoenix. It devours an entire star, killing five billion inhabitants, and ultimately sacrifices itself in atonement during an alien uprising. The movie simplifies "absorbing power" and "personality split" into the same thing, while the comics swap out the host entirely.
Phoenix Force, Chaos Magic, and the Enigma Force: Ranking Marvel's Three Great Powers
The Phoenix Force isn't the only ancient power said to have existed since the dawn of the universe. In the comics there's also the Scarlet Witch's Chaos Magic, and the Enigma Force, which devours galaxies without mercy and can even swallow Galactus himself. Together the three are known as Marvel's Three Great Powers, on par with the six Infinity Stones. The comics are explicit about the power ranking: a fully awakened Phoenix Force is the strongest, followed by a fully awakened Chaos Magic, then Chaos Magic in its normal state, with the Phoenix Force in its normal state ranking last. Interestingly, though the Phoenix Force has the highest theoretical ceiling, it has never actually fully awakened in the comics. Chaos Magic, on the other hand, has awakened once—when an out-of-control Scarlet Witch used it to reset the entire universe—and has cleaned up after the Phoenix Force's messes on multiple occasions. The Scarlet Witch, like Jean Grey, actually started out as an X-Man before later jumping ship to the Avengers. When the Dark Phoenix film was being made, the X-Men film rights were still with Fox, while the Scarlet Witch had already been folded into Disney's Marvel Cinematic Universe—so the two sides couldn't reference each other. That's why the movie only gives screen time to the Phoenix Force and never mentions Chaos Magic at all.
Jean Grey's origin story has itself been rewritten more than once on screen. In 2006's X-Men: The Last Stand, she comes from an intact family, with Professor X and Magneto personally visiting to recruit her into the school. By Dark Phoenix, this changes to her powers spiraling out of control as a child, causing a car accident that kills her mother, after which her father—out of fear—hands her over to the school. The original comics offer a third version entirely: Jean witnesses a friend get hit and killed by a car while they're playing together, and the trauma accidentally triggers her powers to awaken. Her father, a history professor, then turns to his old college friend Professor X for help. All three versions stand on their own, which just goes to show that the character's origin has never really had a single "canonical" telling.
Dark Phoenix was originally meant to be the first installment of an entirely new trilogy, but after Disney's acquisition of Fox, all the planned sequels were scrapped. It went from being the "start of a new series" to becoming, by default, "the final chapter of Fox's X-Men franchise"—which is one reason many viewers feel it fails to live up to the bar set by Logan.
