Twilight has served as Princess of Equestria for over a millenia alongside her sister, Princess Celestia, High Princess of the land. One day, they recieve a note from an unknown source with dubious intent. Their first assumption is that it's a new evil to threaten the peaceful and prosperous Equestria... but they are mistaken. This is not a new evil. It is one which Equestria has faced before, and now, the two rulers must work together in order to prevent it from destroying their home.