During the events of Between Dusk and Dawn Twilight delegated some monster-busting to the EUP. The EUP, not equipped for the job, delegated further. Now, Sunset Shimmer has been drafted into Equestria's forces to deal with the prophesied return of a dread monster. She's going to need to bring everything she's got to fight off the latest threat to Equestria, and the keys may lie in the ponies she hurt before she left.