In 484 A.D., King Arthur (Liam Garrigan) and his knights fight a losing battle against the Saxons. Elsewhere, Merlin (Stanley Tucci) approaches the Knights of Iacon, a group of Transformers hiding on Earth, to help win the war. They hand him an alien staff, before transforming together into Dragonstorm and turn the tide of the battle, but warn Merlin that a great evil will come for the staff. In the present, a year after the Hong Kong uprising, Optimus Prime crash-lands on Cybertron and meets his alleged creator Quintessa. She blames him for Cybertron's destruction and brainwashes him into helping to gain Merlin's staff, which can absorb Earth's energy to restore Cybertron. Optimus is renamed Nemesis Prime. Earth is revealed to be the slumbering Unicron, the ancient enemy of Cybertron and whose horns are emerging across the planet.