On the heels of successfully escaping a deadly digital trap, the members of the Justice League emerge in their own world to discover that Grimm, ravenous creatures from Remnant, have overtaken Earth! In order to defeat the monsters, they must call on their new friends – Team RWBY – for help!

Superman, Batman, Wonder Woman, Flash, Cyborg, Green Lantern and Vixen are transported to the strange world of Remnant and find themselves turned into teenagers. Meanwhile, Remnant heroes Ruby, Weiss, Blake and Yang must combine forces with the Justice League to uncover why their planet has been mysteriously altered before a superpowered Grimm destroys everything.