The Vehicon Faction
Background
The Vehicon faction formed after Megatron conquered Cybertron in the "Beast Machines" series. As the name implies, the Vehicons transformed from robots into -- gasp -- vehicles. This is interesting because there were no vehicle robots in the preceding "Beast Wars" series. All of the Transformers involved had organic beast modes that served to protect them from harsh energon surges that could be potentially fatal. As the Beast Wars intensified, however, both sides became more and more desperate and took increasingly drastic measures to ensure victory. After Megatron attempted to destroy the comatose body of the Autobot commander Optimus Prime, the Maximal commander Optimus Primal took his partial namesake's spark into his body so repairs could be completed on Prime without extinquishing his spark.An unexpected side effect of this gave Primal incredible strength and wisdom along with a new body. Megatron decided he needed backup, so he abducted the spark of his own namesake, put it into his chest, and became even more powerful than before. Unfortunately, the usually cool-headed Megatron also became increasingly unstable.
At this point, you might be wondering why I'm going over Beast Wars history as opposed to defining what a Vehicon is. I'm doing this because it's important to understand the context in which the Vehicons came to exist.
Origin
After the Beast Wars, the surviving Maximals attempted to bring Megatron back to Cybertron for justice. At some point during the ride through space, Megatron fell off of the shuttle to which he was bound and eventually drifted off to Cybertron. Although by this time he no longer possessed the spark of the Decepticon commander, he still had his ideas. One of the original Megatron's ideas was that all organic creatures ought to be destroyed. He saw them as inferior to the Cybertronians. When the new Megatron got back to Cybertron, he arrived with a vengeance. He essentially shut down the entire planet. He removed the spark of every single Transformer on the planet and made it his mission to rid the planet of anything vaguely organic. To this end, he created vast legions of drones that were completely untainted by organic matter. There were three main types of drones: aerodrones (which transformed into sleek, alien fighter jets), cycle drones (which transformed into sleek, alien motorcycles), and tank drones (there was nothing really sleek about these things, but they did look pretty alien). This created something of a conundrum, however; Megatron was an organic transformer himself. He had not shed his dragon mode that he earned for himself after being thrown into a pit of lava. He rarely ever used his beast mode, however. The only times he transformed into a dragon were in times of severe frustration and stress that forced him to give himself over to his most primal and base impulses. This is one of the most important themes of the Beast Machines series: industry vs. nature. This idea was also explored in the Japanese-only series "Beast Wars II," but far less eloquently and well written. To Megatron, organic creatures were "filthy beasts" and that Cybertron was meant to be 'a haven for machines." The guilt that Megatron possessed was one of his greatest psychological weaknesses that Optimus Primal was able to exploit during their battles. (Eventually, however, Megatron's technorganic body was destroyed and his spark inhabited an entirely mechanical giant floating head. Strange, but less hypocritical at any rate.)
The Generals
Nevertheless, he continued to operate his agenda of organic destruction. When the organic Maximals returned to Cybertron, he tried to destroy them, but it didn't quite work. Although Megatron hated the idea of independent thought, he gave three Vehicons life: Jetstorm, Thrust, and Tankor. These three Vehicon generals led the aerodrones, cycle drones, and tank drones, respectively. After the death of Tankor and the defection of Jetstorm, Megatron created two new generals to take their places: Strika and Obsidian. Strika was an incredibly masculine female Transformer who turned into a tank. I bet you'll never guess which group of drones she wound up controlling. Obsidian was a rather nifty VTOL Osprey-looking jet and he commanded the new aerodrones. Strika and Obsidian had been Cybertron's most revered generals and it was their stated mission to protect Cybertron from all forces hostile to its infrastructure. As Megatron was the ruler of Cybertron, their fealty lay with him and thus the Maximals became their enemies.
In the end, only one Vehicon general actually survived the Beast Machines saga: Thrust. Ironically, he was reformatted into an organic creature at the end of the series, much to his bemusement. With all the various drones destroyed, the line of the successors to the renegade Predacons came to an end and Cybertron was transformed into this godawful planet of flowers and grass and preternaturally happy CGI character models.
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