When a pirate named Captain Jack Silver steals the Elements of Harmony, it's up to Twilight and the rest of the Mane Six to get them back. Soon enough they all find themselves on a swashbuckling adventure to find the SEVENTH Element of Harmony.
Before Equestria's founding a small exploration ship was sent to discover new lands should the peace summit fail. The crew returned years later with no memory of what they found. All we know is what was in the journal of the ships chronicler...