Ghostfreak

Appearance
Ghostfreak's first (premature) form is a one-eyed ghost with black lines in which its eye can travel through. Ghostfreak can transform its mass into different shapes and sizes. Ghostfreak's fully developed form is truly more menacing than the Omnitrix form. He actually has a white head, although upside down, his tentacles, hidden underneath the first form are revealed. Spikes grew on his shoulders and through one half of his arms. In this form, Ghostfreak (Zs'Skayr) now has claws instead of droopy hands. The skin he had in his Omnitrix form is presumably a safety feature incorporated by the Omnitrix's creator, Azmuth, both to safeguard this alien from exposure to sunlight and to lessen the frightful impact of its true hideous appearance. This is substantiated by the fact that Zs'Skayr willingly ripped it off, despite it being bright daylight at the time, in order to reveal his true appearance; the true nature of this skin, however, is never fully explained in the series. He also has a form where he is part of Kevin.

Alien Force
Zs'Skayr returned in Alien Force, but Ben absorbed him. Now he's back in the Omnitrix. Although Zs'Skayr took over again, Ben was able to control him. He hasn't been used since.

Appearences

 * The New Albedo Part 2

Ultimate Omnitrix
Ben unlocks Ghostfreak and upgraded him and becomes Ultimate Ghostfreak. He can fire freeze beams and create purple energy bolts from his hand. He is now back in his sun-shield form. He now has green eye and the skin become white.

Misty 10
Ghostfreak appears as a secondary alien in Misty 10, except with a whole new appearance. Ghostfreak's figure has been changed to a female figure with a now curvy body, slimmer arms, a more human-like head, a smaller tail, and the Omnitrix symbol placed on her belly.

Noah 10
He looks the same as UA Ghostfreak, but with darker skin with a blueish tone. He also has an ultimate form.

Ben 10: Alien Team
Ghostfreak is revived, escaped from the Ultimatrix. He now puts a special lotion protecting him from light, though strong light can hurt him. He is also exetemely smart in the series, and is the main villain.

Ultimate Alien
In Ultimate Alien he appears in the episode The Ultimate Sacrifice.

Thorn 10
In Thorn 10 Ghostfreak's chest is bigger and the sun shield is black and it's eye is red. It is unknown what it's true form looks like.

Ben 10: Superverse
Ghostfreak will appear in Ben 10: Supeverse season 1 sometime.