Vilgax is a Chimera Sui Generis from the planet Vilgaxia. He first appears in the first ever episode, And Then There Were 10. Since then he has been the main villain of Ben 10, and the villain in the third season of Alien Force.
He looks like a walking squid type alien. He is tall and green. He has a black suit, which includes spiked armor on his arms and leggs. As for his face, he has red eyes, long green squid tenticles, and two green tubes next to his mouth which help him breath.
so far, he shows no abillities however once we see him actually fight ben we will see what he can do.