Alien X

''"Alien X is the most powerful alien in the Omnitrix. I have to be careful when I use him." -'' Ben Tennyson

Alien X is the Omnitrix's DNA sample of a Celestialsapien from The Forge of Creation. He is considered to be Ben's most powerful alien.

Ben as Alien X
Alien X has a black humanoid body with stars across his body as well as three horns on his head. Compared to his UAF and Omniverse appearances, Alien X no longer has white hands and his green eyes have been replaced with white eyes.

Credit
The picture in this infobox belongs to elmike9.