Tankor's History
Tankor was a Vehicon general who was secretly a reformatted Rhinox. Although initially given a new, dumber personality, the evil version of his original persona eventually resurfaced.
When the Maximals returning to Cybertron from the Beast Wars were infected with Megatron's virus, Rhinox was not as lucky as most of his comrades. While the Transmetals were able to stay mobile for a time, Rhinox was immediately paralyzed and overtaken by Tank Drones. His spark was forcibly removed and stored in a canister in Megatron's citadel.
When Megatron found that he needed underlings to properly control his Vehicon armies in battle, he used Rhinox's spark to power his tank general Tankor. He reasoned that if the Maximals discovered their new enemy had once been their close friend, they would be less willing to fight him. Unfortunately for Megatron, Tankor was only marginally more intelligent than the mindless drones he was created to lead. Meanwhile, Rhinox's spark/consciousness remained intact inside Tankor, albeit unable to act.
After Megatron claimed there were fabulous prizes to be won! for whichever general got the Maximals, Tankor went after them and, after a vicious battle, actually captured them. He then took them to Megatron and demanded his reward, which would be to have his spark removed. Primal managed to use his affinity with the Allspark to contact Tankor's spark and convince him to do the right thing: the Vehicon helped them escape and went on the run with then, but Megatron was able to remote delete the tank's memories of this so he'd be their enemy again. Primal felt something familiar about that spark, though.
The Maximals tried to ambush Tankor to see whether drones would stop functioning without their general; the plan was ultimately unsuccessful due to Rattrap's interference. Tankor received severe damage nonetheless, and had to spend half a solar cycle in a preparation chamber. Once he was operational once more, he rushed out to defend Megatron against the Maximals. But Megatron had made a deal with Rattrap while Tankor was offline, and ordered the Vehicon general to allow the Maximals free passage out of his citadel.
Tankor was part of an attack against the Maximals near a spark-extraction factory. He mostly harassed Rattrap, until he lost track of the rodent. He then turned his attentions to a grounded Nightscream. The two Maximals teamed up to take Tankor out, with Nightscream using his vampiric attack to drain Tankor of his energon.
Tankor was put in charge of overseeing cargo-transfer at a space port. He continuously ordered his drones to work faster, no matter how fast they were already working. Rattrap then got his attention by throwing an explosive his way. This of course got the reaction they had hoped out of Tankor, and the Vehicon general began chasing Cheetor and Rattrap. During the chase, Cheetor tricked Tankor into blowing up a bunch of his own drones. The chase continued until Rattrap got into position to hit Tankor with a crane. Though Tankor wasn't phased from being knocked into the distance, Rattrap managed to hop onto him, and hack into his brain. Accessing Tankor's memories, Rattrap discovered that the Vehicon general had once been his friend Rhinox.
The Maximals woke Tankor's spark, but the Rhinox they got was not the Rhinox they expected. Tainted and embittered by his time inside Tankor, Rhinox rejected the Maximals and embraced Megatron's plan for a "peaceful", technologically-pure Cybertron, only with himself at its head instead of Megatron.
Tankor-Rhinox immediately began plotting against both Megatron and the Maximals. He caught and reprogrammed one of Megatron's Diagnostic Drones, forcing it to work for him. He found the Oracle and, using the Diagnostic Drone, retrieved the Key to Vector Sigma from within. He then faked his own death, seeking to remove himself from both factions' suspicions.
Manipulating events from behind the scenes, Tankor tricked Rattrap into activating an organic rapid-growth catalyst that would make the organics appear much more powerful and out of control, thus inspiring Megatron to take more radical measures to contain them.
His escalating arms race gambit worked in manipulating Megatron into firing the key on a planetary scale—which would have killed all the organics, including the Maximals and Megatron, leaving Tankor to rule a pure mechanical world. Tankor's manipulations failed when he tried to attack Megatron, and a provision against doing so, hard-wired into his programming, shut him down. Due to Tankor's manipulations, however, Primal opened the Plasma Energy Chamber and Megatron fired the Key. The ensuing clash of energies destroyed Tankor's body, and his spark joined the Allspark.
Primal met Rhinox's spark one last time within the Allspark, where Rhinox expressed regret over his recent actions.