Sunset Shimmer made the mistake of playing with things not even Celestia could truly understand. Upon moving through the mirror and into another world - she has compromised the very existence of her human doppelganger, who she has replaced entirely. Living a life far different, but also eerily familiar - Sunset is haunted by her own personal demons and seeks redemption one day at a time. This proves difficult, when she begins to have strange visions of mythical beings that dwell between the two realms, preying on those that wish to travel between the different planes. Pursued by phantom riders in her dreams and morally pummeled by the struggles of troubled teenhood - Sunset is about to discover something that will forever change the fate of two Equestrias.