When a solar eclipse sends a colossal blast of super chilled air towards the earth, it then sets off a catastrophic chain of events that threatens to engulf the world in ice and begin a new Ice Age.

A heroic version of Lex Luthor from an alternate universe appears to recruit the Justice League to help save his Earth from the Crime Syndicate, an evil version of the League. What ensues is the ultimate battle of good versus evil in a war that threatens both planets and, through a devious plan launched by Batman's counterpart Owlman, puts the balance of all existence in peril.

When anti-mutant Colonel William Stryker kidnaps Professor X and attacks his school, the X-Men must ally with their archenemy Magneto to stop him.

In a world where mutants (evolved super-powered humans) exist and are discriminated against, two groups form for an inevitable clash: the supremacist Brotherhood, and the pacifist X-Men.