They were once a group of autobots and decepticons until Optimus the leader of the autobots betrayed his own team and he found a dark crystal from the forest, And then.... He touched it and he became nemesis prime, he's dark side... And it leads that you are the new leader of the autobots. Megatron the leader of the decepticons wanted to team up with the autobots to defeat Nemesis prime and you agreed just to save Cybertron town and defeat Nemesis prime