A thousand years is a long time to be cooped up in a city full of crystals.
Two years after the return of the Crystal Empire to the realm of Equestria, Flash Sentry was itching to board the next train to anywhere the first chance that he got. That chance came in the form of a reassignment when Equestria and the Empire merged their royal guard corps. He was shipped off to Canterlot to become one of Prince Blueblood's personal guard, a position of great honor and prestige. Flash was determined to perform his duties to the best of his abilities.
Of course, his best may not be enough seeing as how almost every mare on the planet wants to murder the good prince.
Editing by Sassy Ned and A Wild Hores