Ratbat was once the Mini-Con representative for the High Council in the days before the great war, and was well known for being corrupt and in the pocket of the wealthy elite. The general opinion was that he believed only what he was paid to, and only while the payment was good. When the war began, he left that position and, along with fellow Council member Contrail, joined Megatron's Decepticons.Nowadays, Ratbat is one of Soundwave's agents, but spends most of his time away from the others. What he does during this time is what he always does best, and that is masterminding incredibly complex financial schemes and scams to drag his targets in the red while he rakes in the credits. And they say war changes people...
Ratbat generally made useless interjections during Megatron and Orion Pax's hearing before the High Council, humiliating Orion when he joked he could imagine an end to their session when the young librarian complained the caste system had rendered the society imaginationless. Ratbat became more serious when Halogen began to concur with Orion and Megatron's beliefs, and was informed that no matter what, it was the beginning of the end for the castes. Ratbat then mentioned attempts to find the Matrix of Leadership had been made by the rebels, and uncharacteristically commented since it had not been found, the Matrix was unwilling to give itself up. This in turn led to the Council's unanimous vote for Orion to become Optimus Prime and be given the quest to find it. An enraged Megatron killed Halogen, declared war and called the Decepticons to follow him. Optimus noticed Ratbat boarded Contrail and left with the Decepticons. During the war Polyhex, Ratbat's home, quickly fell to the Decepticons. Teracycles later, Ratbat's cowardly survival was notable enough for Teletraan-1 to inform Omega Supreme of it.
As the Decepticons raged over the planet, Ratbat negotiated for his survival and became a member of Megatron's army. After the Nemesis departed, Ratbat became commander of the city garrison in Iacon under Shockwave's overall direction. Cowardly and self-serving, Ratbat was of little true use to Shockwave in keeping the peace, but fortunately Shockwave's experiments in social engineering thrived on the chaos Ratbat oversaw in the city.
When a group of Wreckers infiltrated Iacon, Ratbat led a group of Decepticons to capture them at Maccadam's Old Oil House, but was diverted when Omega Supreme began a long-range bombardment of the city as a distraction. Ratbat's fears about reporting his failure to Shockwave became moot when the Space bridge reactivated and the entire planet came under assault by an invasion of Sharkticons. The slimy Ratbat deserted his post at the first sign Iacon was lost, and tracked down the Sharkticon general Tyrannicon to beg for his life and betray the Decepticons. Ratbat led Tyrannicon to the Archives where Shockwave, Alpha Trion and the Wreckers were trying to orchestrate a resistance. Tyrannicon and the Sharkticons would've crushed the Cybertronians then and there if not for Megatron claiming the Sharkticon Matrix of Leadership back on Aquatron. Tyrannicon's forces ran amok, forcing him and Ratbat to flee. Tyrannicon forced Ratbat to show him the way into Shockwave's tower, at which point he abandoned Ratbat.
A traitor with no allies remaining, it's unclear what Ratbat chose to do after that