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.

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.