A telepath, Jean Grey can read minds, project thoughts and illusions into others' heads, and discharge mind-numbing mental bolts. Her telekinetic abilities allow her to levitate herself, other living beings and inanimate objects.

Jean Grey was the first mutant, other than Magneto's own children, recruited to be an X-Man. Jean's parents knew something was wrong with their daughter and, with no place else to turn, contacted Magneto, who had recently announced his intentions to train mutants in the use of their powers. As the X-Men came together, Jean remained their lone telepath. Due to a lack of telepathic teachers Jean was unable to block out many of her teammates' pains and wants. The man whose pain came through to her most glaringly was the mysterious Weapon X. She felt for Logan and these feelings eventually became love.

During a mission, Jean was captured by Prelate Scott Summers. In the months that she was held prisoner, Sinister realized that Jean was an Alpha Class mutant. She was treated as an elite member of the empire and and offered a place in Apocalypse's army, but declined the offer and was sentenced to the Breeding Pens. Sinister would eventually take Jean's DNA and combine it with Scott's to create Nate Grey, a mutant that had the potential to be powerful enough to challenge Apocalypse himself. Magneto learned of this plot and chose to withold his X-Men from rescuing Jean, leaving her in Sinister's hold so he could continue the development of this weapon against Apocalypse.

Without the rest of the X-Men, Weapon X stormed the Breeding Pens and freed Jean, losing a hand in the process. Jean and Weapon X did not rejoin the X-Men but instead fought Apocalypse's forces in Europe. Surprisingly, Sinister contacted the two mutants in order to courier data rods to the Human High Council. The rods contained information regarding Apocalypse's secret plan to annihilate Europe and prompted the Council to launch a pre-emptive nuclear strike against En Sabuh Nur.

While awaiting the Council's decryption of the rods and their impending decision, the two were comissioned by the Council to infiltrate Apocalypse's Atlantic Sea Wall and take out the switching console responsible for monitoring it allowing for the an armada of Sentinels to pass through in the Great Airlift, an attempt to evacuate as many humans out of North America as possible before a nuclear strike.

Although Jean knew it was necessary to take out Apocalypse, she left Logan to warn all she could of the Human High Council's plans to turn Apocalypse's domain into a radioactive wasteland. Once in America, Jean was able to sneak into Apocalypse's kingdom in New York City, by hiding inside of an automated transport and taking out a guard, and sought out Sinister in order to solicit his help in stopping the nuclear air raids. However, Jean discovered that Sinister had already fled from his position in Apocalypse's empire. She was found by Havoc and taken prisoner along with Havoc's brother Cyclops, whom Havoc presumed were working together. They were left in the care of Henry McCoy, the Dark Beast, who was about to subject them to experimentation when they escaped.

Cyclops lead Jean to the location of the Brain Trust, the six powerful telepath minds responsible for inhibiting the prisoners of the Breeding Pens. Pushing her power to its limits, Jean was able to destroy the Brain Trust and free the captives of their mind washing. Afterwards, Cyclops and Jean Grey led the inhabitants of the Breeding Pens in a revolt that saw their emancipation. But, their freedom was fleeting as the nuclear strikes had already started. In a desperate act of preservation, Jean put up a telekinetic shield that could have saved them all from the approaching nuclear warheads, but was killed by a plasma blast from Havoc who had come seeking vengence.

As the bombs fell on New York, the fires of destruction quickly spread on impact. But just as quickly as they engulfed the city, the atomic flames were suddenly pushed back and the nuclear bombs were dismantling themselves. A new power within Jean Grey had been unlocked and resuscitated her body. For a moment, time seemed to stand still as her new power surged and not only stopped a nuclear attack, but saved the entire timeline from being erased. Upon completion, a concussive force was unleashed that rendered almost everyone unconscious and, with her enery expended, Jean returned to a near-death state. The only one who appeared to have witnessed her manifestation of godlike power was Magneto and people concluded that he was responsible for their salvation. Believing Jean to be dead, Weapon X brought her body to Magneto, asking the X-Men's leader to do him the favor of and seeing that she rest in peace.

Months after Apocalypse's defeat, Sinister would return to one of his labs and discover that his instruments had recorded the phenomenon. Jean Grey's powers surged when she saved the world and the timeline and data from the manifestation indicated that she possessed the power of Mutant Alpha that he had long sought; the power to change the world. Sinister dug up and stole her body, but he still needed time in order to learn how to control her power. However, he knew the X-Men would never leave him alone as long as there was though he may still be alive.

He decided that he would blackmail Magneto by threatening to reveal to the world that it was really Jean Grey who saved them all. Exposing their mutant savior as a fraud would instill distrust and put further strain on the already fragile relationship between humans and mutants. In due course, Sinister learned how to control Jean Grey and forced her to use her powers to brainwash others to join him as part of his Sinister Six. With a sizable force assembled and the power of Mutant Alpha at his beck and whim, Sinister believed the time had finally come to destroy those who could prevent him from changing the world as he saw fit: Magneto and the X-Men.

Although the Sinister Six proved to be no match for the X-Men, the power of Jean Grey alone was enough to compensate for their shortcomings. Sunfire tried to match the fire being generated by Jean Grey's newfound powers, but she burned with such intensity that even he could not contain the flames. Weapon X, who had rejoined the X-Men, believed he could reach her and had Rogue fly him closer to where Jean would be able to here his cries. He called out to his former love and pleaded with her to remember who he was, who the X-Men were, and that they were her friends. For a brief moment, Weapon X got through to Jean and this slight hesitation was all the time needed for Nightcrawler to teleport Pyslocke close enough to free Jean from her mental conditioning. She was once again herself and retained all her memories, including those of what Sinister forced her to do over the past year.

At the climax of this conflict, Sunfire fell from the sky and landed on top of Sinister, scorching his body and turning his pale skin black. His burnt body was levitated from the rubble by Jean. She was ready to kill him for what she had done to her, but she was not the only one to suffer at his hands and so his defeat was a pleasure she thought should be shared. Jean and Magneto used their powers to hold him in stasis while crushing his body as Weapon X and Kirika thrust all of their adamantium claws through his body. He suffered a gruesome death for his crimes and the world could now sleep easier knowing that his stain had finally been wiped from the face of the planet.

While the X-Men emerged victorious, Magneto's son Quicksilver and Gambit had both fallen in the combat. Jean apologized as she felt just as responsible for their deaths as Sinister was because it was she who brainwashed the Sinister Six and caused them to side with Sinister. However, Magneto placed the blame for their deaths on himself as it was his fault that Sinister ever took control of Jean Grey in the first place. Despite all this, Jean remained optomistic and was confident that they could put things right and start over again, no matter what happened.

After the funeral for the recently fallen, Magneto went confessed that he was not responsible for averting the nuclear attack against America as previously believed. After admitting to his deception and resigning as Director of Mutant Affairs, Magneto turned himself in to the authorities where he was taken into custody without incident. While incarcerated, Jean Grey used her powers to slip by security and visit Magneto in his jail cell. She offered to use his powers to help him escape, but he declined wanting to face up to his actions.

Jean stopped by to tell him that she would respect his request to stay and lead the X-Men in his place. Magneto thanked her as he felt she owed him no allegiance after his deception. However, Jean saw things from a different light and believed that they owed their lives to Magneto. After the fall of Apocalypse, there were still madmen out there who could have picked up where he left off at a time when people were most vulnerable had Magneto and the X-Men not been protecting the planet from them. He helped make the world a safer place for everybody. She believed that Magneto secretly wanted to help her when he sent Kirika after Weapon X as he knew there was the chance that Weapon X could track down Sinister, expose him, and save Jean.

As Jean was departing, Magneto expressed concern over former comrades that they had lost track of since Apocalypse fell as he had run into Blink and Sabretooth, X-Men they believed to be dead. The X-Men had become so focused on redeeming themselves in the eyes of humans that they had neglected looking after their own. Jean Grey promised that the X-Men would prioritize their location. She returned to the Xavier Institute where the X-Men were anxious to hear of Magneto's condition. She reported that he was a bit worn down from all the burden he had been forced to bear, but seemed relieved to have been given the chance to face up to his actions. She also told them that, though they may be safer today with Sinister no longer a threat, the world would be in need of them soon enough. Nobody knew what tomorrow could bring, so they would just have to wait and see. But for now, they would begin to dream again.