In Transformers One, Orion Pax and D-16 are the best of friends on Cybertron. Joined by B-127 and Elita on a quest to find the Matrix of Leadership, they discover that Sentinel Prime's rule of Cybertron is built on lies and set out to expose their leader.
However, they have vastly different approaches to that; costumed by hatred after learning Sentinel Prime secretly joined with the Quintessons to maintain his power over Cybertron, D-16 decides revealing the truth to everyone isn't enough.
He sets out to kill the villain and, during the fight, accidentally shoots Pax into Cybertron's core. With no one left to oppose him, D-16 murders Sentinel Prime, takes Megatronus' cog, and rebrands himself as Megatron.
Ordering an attack on Cybertron to wipe out what remains of Sentinel Prime's reign - which will likely result in many innocent deaths - Megatron is shocked to see Pax emerge with the Matrix of Leadership. Primus saved him and, as Optimus Prime, he battles his old friend and ushers in a new era for the Transformers as Cybertron's new leader.
As for Megatron, he's banished but enlists the "High Guard," an exiled group of transformers that includes Starscream, Shockwave, Soundwave, and many other future Decepticons.
In the movie's closing moments, after creating the Autobots, Prime restores the Cybertronians' ability to transform and vows to fight for their planet together. If you're a Transformers fan, chances are you can see how this is all building to a sequel which covers the civil war on Cybertron!
As for Transformers One's mid-credits scene, we pick up with B-127 (Bumblebee) as he returns to where he first met Orion Pax and D-16. In a throwback to his introduction, the Transformer reunites with his "friends," some crudely built, lifeless robots who he inadvertently "kills" when showing off his new knife hands.
In the post-credits scene, Megatron gloats about killing Sentinel Prime and, using Megatronus Prime's symbol, rebrands the High Guard as Decepticons and vows, "We will not be blinded by his deception. We are the ones who are Decepticons. Rise up!"
Transformers Two here we come...
Transformers One is the untold origin story of Optimus Prime and Megatron, better known as sworn enemies, but once were friends bonded like brothers who changed the fate of Cybertron forever.
The first-ever fully CG-animated Transformers movie features a star-studded voice cast, including Chris Hemsworth (Orion Pax), Brian Tyree Henry (D-16), Scarlett Johansson (Elita-1) and Keegan-Michael Key (B-127), Steve Buscemi, with Laurence Fishburne, and Jon Hamm.
Transformers One is directed by Josh Cooley and produced by Lorenzo di Bonaventura, Tom DeSanto & Don Murphy, Michael Bay, Mark Vahradian, Aaron Dem and executive produced by Steven Spielberg, Zev Foreman, Olivier Dumont, Brian Oliver, B.J. Farmer, Matt Quig.
Transformers One is now playing in theaters.