In an attempt to travel faster than any pony in Equestrian history, Rainbow Dash attempts a dive from the firmament itself. Upon exceeding the speed of light she is transported nearly 450 years into the future into a sunless, moonless world ruled by the mysterious immortal Thebe.
Badly wounded, Rainbow Dash is recovered by the undying wanderer Anhelios V and her demon associate Bluntforce Gelding. Rainbow Dash is suddenly thrust into a hyper-technological world that she cannot understand, one where she was assumed to have died- -and one where every pony she ever loved has been dead for hundreds of years.
Trapped in this new world with no hope of return, Rainbow Dash collapses into alcoholism and is haunted by hallucinations of a strange, one-eyed golden pony. At the same time, Anhelios V begins collecting the Elements of Harmony for her own sinister purposes.
As the trio crosses modern Equestria, they encounter a number of strange individuals: the immortal soul of Nightmare Moon, an insane computer virus, a cloned supersoldier from a long-extinct warrior race, and a cybernetic lich pulled from the ruins of an ancient city. Each one becomes a potential friend, a potential enemy- -and a potential pawn in a scheme to alter destiny itself.
Meanwhile, creatures from the infinite Beyond surrounding Equestria descend, bringing with them a devastating plague. Their incomprehensible motives bring them in conflict with the goddess Thebe, who decides that the only correct response to the treat is a cataclysmic war of pony extermination.