Princess Celestia and Princess Luna get a surprising visit from a certain pony they thought had long gone with the 2 that ruled before them. That is the reason why Pegasi now rule the sky and the clouds need assistance to move. The reason that, that pony had to go in order to survive. Now after thousands of years in hiding she has come back thanks to the rules being changed by ones she loves.
(this story has one more characters but the thing won't let me put it.)