As the Avengers and their allies have continued to protect the world from threats too large for any one hero to handle, a new danger has emerged from the cosmic shadows: Thanos. A despot of intergalactic infamy, his goal is to collect all six Infinity Stones, artifacts of unimaginable power, and use them to inflict his twisted will on all of reality.

The ultimate X-Men ensemble fights a war for the survival of the species across two time periods. The characters from the original X-Men film trilogy join forces with their younger selves from X-Men: First Class in an epic battle that must change the past; to save our future.