Transformers: The Last Knight

In 484 AD, Merlin finds the Knights of Iacon, a group of Transformers hiding on Earth, seeking their help to aid King Arthur and his knights. They hand him a staff and help Arthur defeat the Saxons, but warn Merlin to hide the staff. In the present day, following the events of Hong Kong, Optimus Prime arrives on the ruins of Cybertron and meets the Cybertronian goddess Quintessa, who brainwashes him into becoming Nemesis Prime and sends him to Earth to retrieve Merlin's staff, which will restore Cybertron by taking Earth's energy core.