The mutant community is outraged when a "cure" is created, capable of transforming any mutant into a normal human being. While some mutants welcome the idea, many others object to the notion of a "cure". Magneto, anticipating a war, assembles a team of mutants to take down Warren Worthington II and his "cure". However, the X-Men face a daunting challenge as Magneto has a significant advantage: Jean Grey, who has joined him, has the Dark Phoenix within her, granting her the power to destroy anything in her path, including her own teammates.

X-Men: The Last Stand
As the government closes in on a cure for mutations, Jean Grey's powers as the Phoenix intensify, leading her to join forces with Magneto in a quest for mutant dominance, which ignites a catastrophic war between the X-Men and their enemies.