Before they became bitter enemies, Optimus Prime and Megatron were once friends. What went wrong? The fractured relationship is teased in Paramount’s new trailer for Transformers One.

Set on Cybertron, “Transformers One” is the origin story of how Optimus Prime (voiced by Chris Hemsworth) and Megatron (Brian Tyree Henry) go from the closest friends to sworn enemies.

Megatron is standing on a black and brown striped background above text saying “Transformers One.” Above the rectangle framing the image, more text says “Optimus Prime” above the image ...

New beginning. Which is to say: origin story. Way back before people appeared on the scene and before Optimus Prime and Megatron were sworn enemies, there was Orion Pax and D-16, lowly miner bots ...

a.k.a. Optimus Prime (Chris Hemsworth), and D-16, a.k.a. Megatron (Brian Tyree Henry), and their complicated history on planet Cybertron three billion years prior to the core "Transformers" narrative.

The previous trailers for Transformers One have played up the friendship between Orion Pax and D-16 before they respectively became Optimus Prime and Megatron. But in the newly released final ...