In 2012, Bill Cipher was defeated-and the entire universe was thrown out of whack. Years later, the fate of six realms hangs in the balance as a group of desperate tweens, teens, and barely-adults try to discover who they are and how they can stop the apocalypse. Gravity Falls/TOH/Amphibia/Big City Greens/SVTFOE/TGaMM crossover. This is gonna be a long one, folks.