King Sombra is the last cave unicorn alive, is a male unicorn, the former tyrant ruler of the Crystal Empire. Princess Celestia tells Twilight Sparkle that he took over the Crystal Empire a thousand years ago, but was banished into the frozen north. King Sombra put a curse on the Crystal Empire which made it vanish into thin air. When the Empire returns, so does King Sombra, who attempts to retake it. He is defeated by the Crystal Ponies' use of the Crystal Heart, but his horn survived.