Rainbow Dash has returned to Equestria, and nothing makes sense. She knows the pegasus that visited her, but if Rainbow had been gone for ninety two years, she should be dead. And she knows that purple unicorn, but she should be an alicorn.
Rainbow Dash has become an alicorn Princess, but there's still so much that she needs to do. A cutie-mark-removing unicorn, out of control vines that even Discord can't stop, and a power-hungry centaur are just the start.
Nightmare Moon was the first pony in space. The next documented pony in space was Princess Celestia, from when she had been sent to the sun when Nightmare Moon returned. There was a pony before Princess Celestia who went into space, but who?