Celestia has been keeping a close eye on her once wayward sister Luna, but that hasn't stopped Luna from plotting her demise (and the demise of the Elements of Harmony) in absolute secrecy. After three-years under house arrest in the castle, the first steps in her plan to overthrow Princess Celestia have been set in motion, on the night of a full moon, as she schemes to take the throne and bring the lands of Equestria to everlasting night once again, and killing all who stand in her way.