From: One Shall Rise, Part 1 and One Shall Rise, Part 2
As Optimus Prime investigates the site of another quake epicenter, Unicron manifests an avatar in order to make himself known to the last Prime.
aeonmagnus.tumblr.com/post/109...
Optimus Prime makes short work of each of Unicron's avatars, in some fantastic fighting action. However, it's ultimately a numbers game; with an unlimited number of avatars available to Unicron, it's only a matter of time before the Prime lineage will come to an end...