On Earth-838, where reality is an intricate web of dimensions, the X-Men have maintained peace between humans and mutants, however, a sinister force rises in the shadows. Mister Sinister, a ruthless mutant geneticist and master of genetic manipulation, plans to unleash a catastrophe that threatens all known realities.
As the X-Men struggle to contain the threat, a secret group called the Illuminati arrives on the scene. Composed of some of the greatest minds in the universe, including Doctor Strange, Tony Stark (Iron Man), Reed Richards (Mr. Fantastic) and others, the Illuminati reveal that Mister Sinister can destroy not only Universe 838, but also all the other realities connected to the Multiverse.
The X-Men, together with the Illuminati, embark on a dangerous journey through interconnected dimensions, facing alternative versions of themselves and challenges that defy reality itself. They must stop Mister Sinister before he achieves his goal of triggering a multiversal crisis and undoing the cosmic order.
