Break a glass, any glass, and watch the shards as the fall effortlessly to the ground. Each little shard, no matter how big or small is another reality. Each one tells a different story, of how events play out differently, of how relationships and moral understanding change. And it all happens as they watch on, connected to our worlds by those who accept their fates and brought into them by those who chose their own.
The shard closest to your world of ponies, that is our world, that is Noella Equestria, Where anthropomorphic animals live alongside equally anthropomorphic ponies, magic and technology co-existing in harmony and the world knows nothing but peace, aside from the trend of fighting that spans the entire world. However, before animals and ponies were common, there were dragons, and with that, there was a war waged by the two sisters who felt they were a threat. Now after all those years, all that remains is one, Spike the Dragon, who finally returns to his childhood home after 10 years.