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.

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.