Quickfire Storyline: Optimus Prime/Orion Pax
Optimus Prime wasn't always the inspiring Autobot presence he's known for today. As young Orion Pax, he worked under the tutelage of Alpha Trion... but not as a future Prime. Instead, Orion was working to become an archivist, to help preserve what little knowledge remained from the Golden Age of Cybertron. (This was during a lull in the war, when the Decepticons lacked an active leader.)
Pax was diligent in his studies, and filled his own memory stores with every new scrap of information he could get his servos on. One would think he'd be well-behaved too, but no such luck. When he wasn't reading or working his apprenticeship, he liked to explore the abandoned cities of Cybertron with his closest friends; Jazz, Ariel, and Megatronus.
They all became quite infamous for their schemes to sneak out, and Orion was seen as bad influence on the Prime Protege, Megatronus... until they started to uncover ancient tech that had been long lost to the wastelands. Together they uncovered several ways to make use of the solid deposits of energon deeper in Cybertron's core, and helped usher in some new hope for Autobot civilization.
But of course, it was too good to last.
On the day Megatronus was to be appointed Prime, the Matrix of Leadership rejected him. In the ensuing confusion and chaos, Megatronus learned the truth about his origin as a Decepticon protoform, and lashed out against Alpha Trion for setting him up for failure. Orion came to Trion's defense, and during the fight, the Matrix chose him as Primus's new champion, and transformed him into Optimus Prime.
Megatronus fled with a few other defecting Autobots... That day, he became Megatron, and the newest era of the war had begun.
But that was thousands of years ago. The War has finally come to an end. A ceasefire had been called, and by none other than Megatron himself... Optimus should be happy, and without a doubt he is relieved that the fighting is finally over.
... but one of the agreements of the ceasefire was very clear... both Optimus and Megatron had to step down from their positions as leaders.
Optimus has given a lot during the war, and has held the entire weight of the Autobots' fate on his shoulders for so long... He's not sure he remembers how to be Orion Pax again... especially not when there is still so much work to be done.