To celebrate Twilight Sparkles coronation Celestia, Luna, and the rest of the Mane 6 get together to enjoy a night of friends and drinks at the library. That only lasts long enough for the alcohol to make clubbing seem like a good idea.
A malicious force has brought something to Equestria that has been sealed in Tartarus for centuries. Will Equestria be able to weather the coming storm or will the Spirits and their hosts destroy the way of life everypony hold so dear?