All of the missions involved with World War X. The plot follows below.
The game begins with Luigi and Batman being sucked through a portal during the naval battle in Fighters of Lapis, where they land in a war zone. Batman and Luigi are suddenly chased by a hot pink tank, and Luigi trips, where two soldiers grab him and Batman. They force brainwashing on the two, turning Luigi into Mr. L. Batman manages to say "Zur-En-Arrh" to turn his mental state into Batman of Zur-En-Arrh, which he seems to prefer over being brainwashed by them.
Batman of Zur-En-Arrh comes across a rebel group led by Homura with it's members including Mako, Don-Chan, Kodama, Homura, Player, Joanna Dark, and Rumble McSkirmish. Batman of Zur-En-Arrh gets the impression that he needs Luigi and escape although he's not sure why.