A letter is received to Sky Warrior, a 2,000 year old commander and as ageless as any Alicorn, that was written by the Princess. Upon hearing the news that he shall go to the Crystal Empire to protect them sounds a bit stupid even for Princess Celestia. There must be some reason as to why she sent him there and why she would send him as I quote, "to protect a bunch of worthless ponies." Well, he's in for the ride of his life when he finds out they are anything but worthless.