The Crystal Empire is located in the Far North of Equestria. The Crystal Empire was enslaved by a former ruler named King Sombra. His reign came to an end after Princess Celestia and Princess Luna attempted to free the Crystal Ponies, however not before Sombra had placed a curse on the kingdom causing it to vanish for a thousand years. A thousand years later the Empire returned for an unknown reason along with it's former ruler King Sombra. His attempts to recapture the Empire were foiled by Twilight Sparkle and friends. Today the Empire is ruled by Princess Cadance and Shining Armor. The Crystal Empire is protected by a Crystal Heart, which is powered by the love of the Crystal Ponies.
This is where users can list their characters who live in the Crystal Empire below.
GalleryPictures of the Crystal Empire.
Crystal Empire (Link to MLP Wiki)