King and High Lord Horatio Sin Ambrosius of the Royal Vampiric Empire of Avalon, along with his girlfriend Toya, her father Robert, and the vampiric ambassador Alex all share a mysterious dream in which they've become ponies. They quickly realize that it's far from a dream, however, and learn that the vampire was brought to Equestria by a lonely Princess Luna seeking true recognition for her beautiful night.
Upon meeting the princess she develops feelings for the fully-nocturnal and sensitive Sin, her jealousy once again becoming a problem when she realizes his dedication to Toya. Will the four newcomers along with Celestia and the Elements of Harmony be able to keep her emotions in check and prevent Nightmare Moon from taking over once more?

//Subject to change. My first MLP story, so sorry if it isn't too great ^^'