Every year, Jewish, Christian, and Muslim ponies set out on a long trek all over Equestria to build comraderie between the different faiths of the book. By this point, there are no surprises: it's a long walk of friends chatting to each other and nothing really faith-shaking happening for nine days.
This year, however, things are different.
This year, the Fair Folk, sealed away by Princess Celestia, steal the pilgrims away, including all of the former bearers of the Elements of Harmony, suppress their powers, and put them to work as cheap labor. Their hopes for escape lie with one baby dragon, but even then, they can only pray for to be delivered.