When a suspicious interdimensional portal opens up right in the Royal Canterlot Castle, Princess Celestia quickly invokes the Elements of Harmony to help her, only to find nothing more and nothing less than a 16 year-old male human with a mysterious technologic device on his wrist , which allows him to transform into a huge variety of powerful, extraterrestrial beings.

But that human is not the only thing that has arrived to Equestria...