-Doctor Xeros was a Quintesson physician assigned to the planet Aquatron and employed by Inquirata as his right-hand man. Like Inquirata he was disguised as one of the Cybertronian natives in order to fool the arriving Autobots and Decepticons, but his true nature later became known.
A studier of alien life, Xeros found that most species in the galaxy was mechanical in nature and was amazed to find how short-lived organics were. After the Quintessons found and annexed the lost Cybertronian colony of Aquatron, Xeros was assigned to it though he longed for a posting on Quintessa. When the Autobots were due to arrive at Aquatron, via manipulations sent out by the Sharkticon Matrix, Xeros followed Inquirata's lead and adopted a Cybertronian disguise.
After Optimus Prime suffered a "fainting spell", he was brought to Xeros so the physician could examine the Matrix of Leadership and beam data on it back to Inquirata. His overzealous examination of the Prime however aroused Jazz's suspicions.
Soon after the Quintessons' true motives came to light, Optimus Prime and Megatron agreed to a temporary alliance to overthrow the Quintessons prompting Xeros to run and hide in Inquirata's inner sanctum. The two leaders found him however and he revealed he knew nothing of Inquirata's whereabouts. In frustration, Megatron punched a random control panel which revealed the Sharkticon Matrix. Over both Optimus and Xeros's protests, Megatron inserted the Matrix into his chassis, the power boost allowing him to overpower both Optimus and Xeros. While Optimus survived, Xeros was devoured by the Sharkticon hordes.