After the Decepticons discover energon on a distant planet, Optimus Prime and the Autobots arrive in Ponyville, quickly attracting the crown's attention. Now it is up to Prime and the princesses to protect Equestria from the Decepticons.
Three years have passed since Optimus left Equestria, a decision he will come to regret. In his absence, the Decepticons have returned, ready to claim revenge on the planet that slew their leader.