In the sequel X2 (2003), Raven uncovers evidence of William Stryker's plan to build a second Cerebro and then help Magneto escape his plastic prison by seducing one of his guards in her human form and injecting him with excess iron; Mystique and Magneto then join the X-Men in foiling Stryker's plan to use his own mutant son Jason to trick Professor X to telepathically slaughter the world's collective mutant population with Cerebro #2.

Unknown to Raven, Magneto, and Professor X, the events of The Last Stand and her earlier assassination of Trask and capture in 1973 eventually lead to a dystopian future where mutants are hunted to near extinction by unstoppable super-Sentinels partially created from her DNA.

A distraction from Logan and Beast allows Raven to knock Magneto out and save Nixon; she then considers going through with killing Trask anyway, but is talked out of it once and for all by Charles.

Her saving the president, along with sparing Trask and the latter being prosecuted for trying to sell US military secrets to Vietnamese government officials, leads to the cancellation of the Sentinel program and the Days of Future Past timeline in 2023 being unmade.

[6] Jennifer Lawrence signed a contract for three films but also returned for Dark Phoenix, stating that she did not want to leave her character's fate hanging.

[10] In February 2022, during an interview with ComicBook.com about her work on Star Trek: Strange New Worlds, Romijn expressed doubts as to whether Marvel Studios would wish to bring her back as Mystique or not for the Marvel Cinematic Universe in light of Patrick Stewart's then-upcoming reprisal as Professor X in Doctor Strange in the Multiverse of Madness (2022), but stated that she would be open to reprise her role as Mystique if she were offered to return due to how much she enjoyed working on the X-Men films.

[11] In order to prepare Rebecca Romijn-Stamos for playing the role, the special effects makeup team covered her with silicon prosthestics on three quarters of her body, with the remaining spots being painted blue.

The change in prominence has been explained as partially being due to Jennifer Lawrence growing fame since X-Men: First Class, starring as the main heroine Katniss Everdeen in The Hunger Games (2012) and winning the Best Actress Oscar award for Silver Linings Playbook (2012).

In the new timeline created with Days of Future Past, this never happens and she instead saves the president and becomes a reluctant hero to humans and mutants alike, especially to Storm and Jean Grey, who both state her to be an idol to them.

The comic book version has been noted for having slowed or possibly even halted aging due to her unique physiology; whether she has this ability in the film series has not been explained.

[26] Sean O'Connell of CinemaBlend wrote that in X-Men: Days of Future Past, Mystique "is treated as a significant threat to this on-screen universe, but her motivations are muddy, at best".

[27] Steve Rose of The Guardian said that Mystique is "key to the success of the mission, but despite being able to alter her appearance however she wishes, she's obliged to spend most of the film prancing around virtually naked save for blue body paint".

[36] An action figure of Mystique from X-Men: Days of Future Past was displayed on Chicago Comic & Entertainment Expo in 2014,[37] but was later announced to have been cancelled from official release after Jennifer Lawrence did not approve of licensing her likeness.