When Twilight Sparkle decided to go to Moondancer's party instead of the Summer Sun Celebration, the entire world is thrown into disorder, and Lyra, Bon-Bon, Muffins, Octavia, Zecora and Pip are all that stand between Equestria and eternal night.
In the dark waters, you see a shape begin to take form. A hideous figure emerges from the swamp, and points to you with a single, calloused finger. "Hey mate, you going to finish that sandwich?"