Sentinel Prime is the original Autobot leader before Optimus and taught him the values of life and honor to the end. He was the most powerful Autobot in existence before his death at the hands of his pupil, Optimus Prime. He betrayed the Autobots and became a Decepticon; so that he could save Cybertron.
Dark of the Moon film Edit
On the planet Cybertron, there was a great war that practically destroyed Cybertron. Wanting to save his dying homeworld, Sentinel secretly made a deal with Megatron to help him recreate Cybetron in the name of the Decepticons. Megatron told him to take his space bridge-forming Pillars to the planet Earth and they'll recreate Cyberton here. Sentinel flew away in a ship called the Ark that carried hundreds of Pillars. Sentinel was supposed to warp jump on Earth so he and Megatron could recreate Cybertron. However, Decepticon Orbital Assault Carriers dealt heavy damage towards the Ark, resulting in Sentinel Prime accidentally crash-landed on the dark side of the Moon. This also resulted in Sentinel Prime entering in stasis lock.