In an different universe, Celestia has destroyed all of the territories outside Ecuestria, with no Mane 6 or other force to opose against her tyranical rule, when she decides through an anonimus "source" to go and destroy other timelines and other universes, mainly ones in which she went different directions with her rule, our heroes will have to face her and her allies to save the multiverse and everyone else once Celestia and others rule extends.