An ancient, eon-old satellite has orbited Equus for millenia, since before Equus, even. Its a wonder that it's even there, and even more of a wonder of how it even exists. It predates even the princess rulers of Equestria.

It's presence was discovered millenia ago by an ancient philosopher, and finally, nearly half another millennium after Luna's return, the ship is finally being accessed, thanks to most recent advances in technology.

"One small step for Equestria. One giant leap for Equusian kind."