Vilgax is an intergalactic conquerer from the species Chimera Sui Generis from the planet Vilkgaxia (which he conquered and named after himself) who serves as the main antagonist and most recurring villain in Ben 10 and Ben 10 Alien Force, he has yet to appear in Ultimate Alien. Vilgax's goal is to obtain the Omnitrix and use it to create an army of shape shifting drones in order to take over the universe. Though he originally just wanted to steal the omnitrix from Ben not really caring what happened to Ben once he stole it, after failing several times and being imprisoned in the Null Void because of Ben he grew to hate him and in his last appearance he seems to want to kill Ben just as much as he wants the Omnitrix.
- Vilgax is quite similar to Cthulhu both in appearance and plan to conquer the universe.
- In the original series Vilgax knew the secrets of the omnitrix but in Alien Force he couldn't even use the alien selector this is because Ben changed the codes (Azmuth taught him how) and made some unknown changes so that Vilgax wouldn't be able to use it.
- Most Chimera Sui Generis have green eyes (as shown in Ghost Town) but Vilgax has red eyes this is most likely because of his laser vision ability.