trap set by the group, while many of the other Autobots, including Ratchet and Leadfoot, are slain. An inventor, Cade Yeager, comes to Prime's aid and helps restore his health. After uniting with a small band of Autobots, Optimus faces Lockdown, a ruthless assassin and bounty hunter allied with the humans, and KSI, an organization that produces man-made Transformers. Optimus is captured by Lockdown, but the Autobots rescue him. Optimus is quickly losing faith in humanity, but at the urging of Cade, chooses to stay and fight Galvatron (a resurrected Megatron) and his new army. Prime releases the ancient Dinobots, and rides a newly tamed Grimlock into battle through Hong Kong. He kills Lockdown and Harold Attinger at the film's climax, avenging his friends, such as Ratchet and Leadfoot. At the end of the film, he leaves Earth and flies off into deep space, seeking to find out the truth about his mysterious Creators. Optimus Prime returns in Transformers: The Last Knight, which is set three years after the events of the previous film. Having been frozen in the vacuum of space, Optimus has been drifting on the far reaches of the Earth's solar system for some time. However, he later crash-lands on Cybertron, its atmosphere reviving him. He then confronts the being currently in control of the planet, a powerful sorceress named Quintessa, who confesses to be the maker he is searching for. Optimus is easily subdued by Quintessa, who convinces him that he destroyed Cybertron and reveals that the Earth is actually Cybertron's "ancient enemy" Unicron. Redubbing him "Nemesis Prime", Quintessa brain-washes Optimus and tasks him with retrieving her stolen staff, with which she plans to drain Earth/Unicron's life force so that Cybertron can be restored. Nemesis succeeds in retrieving the staff, but is hindered by Bumblebee, whom he engages in a fierce duel. Nemesis nearly kills Bumblebee, but when the normally mute Bumblebee suddenly speaks, urging Prime to remember who he is, the sound of his oldest friend's voice is enough for Optimus to return. However, Megatron, revealed to be in league with Quintessa, swoops in and steals the staff from Optimus. Prime is then attacked and sentenced to death by the Guardian Knights for aiding Quintessa, but he is saved by Cade Yeager, who convinces Optimus to help him save Earth. Optimus leads the Autobots in the attack on Quintessa's lair, during which he slays the