Avalon (planet)

From Tardis Wiki, the free Doctor Who reference

Avalon, a planet with six moons, was discovered near the end of the Earth Empire. Once home to an advanced race, it was colonised by humans, setting up a nation named Elbyon. The First Doctor visited Avalon circa 3025. (PROSE: The Sorcerer's Apprentice)

Using nanomachines and a nova trigger, they attempted to force the Empire's planets to stay together towards the end of the Empire, though they were unsuccessful. (PROSE: The Dark Path)