Optimus Prime comes to Earth to gain control of the Allspark and defeat his brother-turned-enemy Megatron.

"The year is 2005, and the Decepticons have retaken Cybertron from Optimus Prime and his Autobot warriors. Both sides are seething with anger, and that hatred has blinded them to a hideous menace headed their way. That menace is Unicron, a monster so powerful he devours planets. Unicron has chosen to take control of Autobot Matrix for his own evil purposes, and to accomplish this he has created a force of super robots. ... With Decepticons on one...

Unicron has been defeated, but his destruction has created a black hole, which is threatening the Autobotsb2s home world of Cybertron. Itb2ss up to Optimus Prime, his team of heroic Autobots and their new human friends, Coby, Lori and Bud, to secure the four mystical Cyber Planet Keys, in order to destroy the black hole. Unfortunately, Megatron and the Decepticons are always lurking. And if the Cyber Planet Keys fall into their hands, it could mean...

The Transformers' War on Earth ended years ago. Dot Malto, a veteran of the war, along with her husband, Alex, and their kids, Robby and Mo, move to the remote town of Witwicky, Pennsylvania, to start a new life. But Witwicky proves to be more than meets the eye and the family soon finds their lives intertwined with the Terrans, Twitch and Thrash, the first generation of Transformers robots to be born on Earth! When the evil half human/half robot...

Four million years after crash-landing on an unfamiliar planet, sentient robots with the ability to disguise themselves as common vehicles awaken on present-day Earth. Engaged in a crucial race to find a new energy source for their home planet of Cybertron, Optimus Prime and the heroic Autobots must defend the innocent people of Earth against their archnemeses, Megatron and the power-hungry Decepticons.

Optimus Prime is highly upset when he discovers Transformers technology has been on Earth since the early 1960s, when the ship that carried his mentor, Sentinel Prime, and the technology that would have brought peace to Cybertron crash-landed on the Earth's moon. Optimus Prime urges the United States to send another mission to retrieve that technology before it can fall into Decepticon hands.

The world was saved after an epic battle that left a great city torn. As humanity picks up the pieces, a shadowy group reveals itself in an attempt to control the direction of history, while an ancient, powerful new menace sets Earth in its crosshairs. With help from a new cast of humans, Optimus Prime and the Autobots rise to meet their most fearsome challenge yet. In an incredible adventure, they are swept up in a war of good and evil, ultimately...

The Autobots and their allies are shocked when Sentinel Prime reveals he has made a deal with the Decepticons and turns on them. Sam discovers a human traitor as well when Carly's boss kidnaps her in order to force Sam to discover and reveal Optimus Prime's plans for fighting the Decepticons.

Humans and Transformers are at war, Optimus Prime is gone. The key to saving humanity's future lies buried in the secrets of the past, in the hidden history of Transformers on Earth.