The Anti-Monitor is one of the non-playable characters in LEGO Dimensions 2: The Rise of Enoch, from the DC Comics franchise.
The Anti-Monitor was born at the beginning of the multiverse on the anti-matter universe planet of Qward and was known as Mobius, creator of the Mobius chair that soon came under the ownership of the New God Metron, eventually Mobius was able to tap into the power of the Anti-life equation becoming Anti-Monitor and serving as the representation of all evil and anti-matter in the multiverse. As such, he has frequently served as a powerful adversary for the entire multiverse, conquering the anti-matter universe then attempting to destroy all existence during the "Crisis on Infinite Earths" story arch.
Grand Interdimensional War
Anti-Moniter is one of the most powerful villains that joined Enoch's army. He is hired by Grand Emperor Enoch to destroy everything that exists, making him believe that the Anti-Monitor would help end the war early.
He is later seen during the Fate of the Multiverse alongside Doomsday where they fight Superman and Supergirl. They later get sucked into the vortex after the end of the Grand Interdimensional War.