In the year 2005, after years of conflict between good and evil, the Autobots have finally driven the Decepticons off Earth. However, Megatron leads his forces to invade the Autobots' homeworld, Cybertron. Optimus Prime leaves Ultra Magnus and other warriors to defend Earth, while he takes a team to establish a secret base on two moons near Cybertron, planning to deliver a decisive blow to the Decepticons. But the plan is discovered by the Decepticons, and Megatron launches a preemptive strike against the Autobots on both the moons and Earth. During the battle, Optimus Prime tragically sacrifices himself, and Megatron is severely wounded. In his final moments, Optimus Prime passes the Matrix of Leadership to Ultra Magnus. Meanwhile, the evil Unicron, seeking to destroy the Matrix that stands in his way, saves Megatron—who was betrayed and abandoned by Starscream—and rebuilds him into the more powerful Galvatron. As new leaders emerge for both the Autobots and Decepticons, the war between good and evil escalates to new heights...