Spoilers ahoy! Proceed with caution! *here there be spoilers!* When Optimus Prime, believing he is Orion Pax, looks himself up in the archives he is shown an image of a yet unnamed Transformer. I didn't think anything of it at first, but the more I look at him the more I believe this to be Ultra Magnus. I mean just look at the attached images and tell me you don't see how they could be Prime's version of Ultra Magnus.