Long ago the Quintessons created a new generation of machines. These were, to date, their most complex creations. However the same breakthrough that allowed their megacomputer, Vector Sigma, to come up with the Autobot and Decepticon lines of merchandise came with a flaw. They were alive. In a bid for freedom the sentient machines launched a rebellion against their cruel masters. The rebellion died alongside the leader of the rebels at the time. A3.
Vector Sigma was reprogrammed so no further incidents of sentience would be possible and, with their upgraded lines of non sentient machines, the Quintessons quickly cornered the galactic markets from the comfort of their home planet of Cybertron.
There are rumours that not all of the Autobots and Decepticons from that rebellion died with their leader. There are tales that the fight continues to this day and, over the years that passed, the Autobots and Decepticons used their unique powers of transformation to avoid destruction at the clawed fists of the dreaded guardian robots or the razor sharp teeth of the Sharkticons.
In fact all prepare for the day that a second battle dawns and the fate of the Transformers, Quintessons and Cybertron is finally decided.