Chimera Sui Generis
Chimera Sui Generis are creatures that live in a place only known as the Null Void Frontier later renamed Vilgaxia. They are large aliens with incredible strength. Both male and female of this speices have long tendrils lik e those of an octopus or squid, most females appear to have them on there head, while males on there chin, though females have "beauty marks" on their face. They are native to either the Null Void Frontier or the Shadow Realm. Chimera Sui Generis are blessed with incredible natural strength enough that Myaxx, a non-warrior member of the species, was able to tear battle robots apart with her bare hands. Certain members of the species have been shown to have amazing endurence, before being enhanced, Vilgax survived a nuclear explosion at point blank range, though he was largely believed dead after this.
Vilgax
Vilgax has mentioned that his people are not warriors like him, although the stature of an unaugmented specimen, Myaxx, suggests otherwise. It would seem then that Myaxx's cowardice may be a natural trait among the species, and is lost on Vilgax, possibly relating to his apparent insanity. The members of the species shown in detail, Vilgax and Myaxx, are known to be extremely intelligent, Vilgax having a vast knowledge of the Omnitrix and robotics while Myaxx was one of those who helped make the Omnitrix in the first place as well as the cloaking field protecting Xenon.
Female
It is unknown if this is a representation of the species as a whole. Chimera Sui Generis also have the ability to transform into large octopus-like creatures at will, which is described as their "true" form, though it would only be useful in water. This may hint to the habitat they live in and their humanoid change in appearance.
It is not known if all Chimera Sui Generis live in the Null Void Frontier, but it is known that Vilgax was born there. In "Alien Force" they live on a planet called Vilgaxia , though its likely it was renamed in Vilgax's honor (the saving of his homeworld from Ectonurite invaders) or it was changed during Vilgax's Conquering of 10 Worlds (which his homeworld would have most likely been the first).
Known Chimera Sui Generis:
Vilgax - Main Villain of Ben 10, returns in "The Vengeance of Vilgax". It should be noted that Vilgax is a cybernetically altered Chimera Sui Generis and differs greatly from the appearence of the species as a whole. He is also the king of their species and, according to him, the sole warrior on his planet.