When Unicron threatened Earth, Optimus Prime had no choice but to surrender the Matrix of Leadership in order to stop Unicron. However, due to the loss of the Matrix of Leadership, Optimus not only lost the collective wisdom of the Primes but also lost his memory of events following his conversion from Orion Pax. As he and Megatron had formed a temporary alliance, to stop Unicron, Megatron was the first to notice Optimus' amnesia. He, therefore, took advantage of this and brought "Orion" along when Soundwave opened a ground bridge to the Decepticons' warship. Megatron then told Orion half-truths about the Decepticons and the Autobots, thus tricking Orion into serving the Decepticons' cause.