Zs'Skayr

Zs'Skayr was the Ectonurite High Ecto-Lord of Anur Phaetos. He originally was stuck in the form of Ghostfreak, but after time managed to gain control over it and escape the Omnitrix, becoming one of Ben Tennyson's most dangerous enemies.

Appearance
In the original series, his body is grey and he has black nails, black lines on his chest. In Alien Force, his body is purple/blue and he has white nails and his spine is sticking out of his back and he still has black lines on his chest.

Powers and Abilities
Zs'Skayr has intangibility and invisibility (accompanied by an inverted color scheme and transparency).

Zs'Skayr can control his density.

Zs'Skayr can change into a smoke like form.

Zs'Skayr can peel back his skin, which reveals his tentacles.

Zs'Skayr can shoot a powerfull energy beam, if his skin is peeled back.

Zs'Skayr can possess life forms and take full control over them.

Zs'Skayr possess powerful telekinetic abilities, the extent of which is still unknown.

Zs'Skayr can absorb the powers of other living things having already absorbed Ben and planned to absorb Vilgax's powers as well.

Zs'Skayr is able to transform living creatures into Ectonurite minions (with the appearance of the Sun-shielded Ghostfreak).

History
The original Zs'Skayr was High Ecto-Lord of Anur Phaetos. He learned about the Omnitrix when one of Vilgax's data probes crash landed and he read its data files. Not long after, he met up with Myaxx when she was scouting the planet for DNA samples and aided her in acquiring samples from the nearby planet of Flors Verdance; however, unknown by Myaxx, Zs'Skayr possessed the Florauna that was being sampled and thus Myaxx then got a Ectonurite-Flouarana hybrid sample. Zs'Skayr's personality lay dormant within the Codon Stream, as Ectonurites' consciousnesses exist even in a single strand of DNA.

Original series
His mind lay within the DNA sample of Ghostfreak. He finally managed to force his way out of the Omnitrix in the episode Ghostfreaked Out. After peeling off the protective layer of skin that normally covered him, he tried to take over Ben's body in order to become whole again. After a failed attempt to possess Ben, he found the Circus Freak Trio (whom were attempting to steal gold trophies from where Ben was at merely minutes before freeing himself) and coerced them to help him by taking over Thumbskull and tossing him about like a ragdoll in the room the three of them were hiding in. He was defeated when he was exposed to sunlight by Ben, causing him to burst into flames. Following this, Ben was unable (and unwilling) to turn into Ghostfreak again.

Zs'Skayr is the main antagonist in the third season, returning in the two-part episode The Return and Be Afraid of the Dark where he is revived by an alien scientist named Dr. Vicktor, a Transylian from the Anur System that had stolen material from Zs'Skayrs' clocktower grave to re-animate his deceased master again. Gathering a group of horror-themed aliens as minions, Vicktor enacted his plan to resurrect Zs'Skayr, whose then planned to plunge the Earth into total darkness for him to control. Zs'Skayr himself is still intent on gaining control of the Omnitrix. Using Corrodium retrieved by the mummy alien in Under Wraps they set up a Corrodium beam that will block out light from the sun, allowing Ghostfreak to exist in eternal darkness. Ghostfreak succeeds in doing so, allowing him to reach his full potential, but only for a while before Doctor Viktor accidentally rammed Max Tennyson into the projector during a dogfight. In the end, Ghostfreak is killed on board a space shuttle, when Max opened the shuttle's roof and exposes him directly to the sun. Ben regains use of the form during this time, except in the Ectonurites' natural state.

Ben 10: Alien Force
Zs'Skayr reappeared in Ghost Town. After being removed from the Codon Stream, Zs'Skayr had apparently been imprisoned by the Galvans. Vilgax frees him on the condition that he tell him the secrets of the Omnitrix and the knowledge to defeat Ben, but Zs'Skayr betrays him and takes over Vilgax's home planet of Vilgaxia, possessing the citizens and turning them into his minions that resemble his sun shielded form. Vilgax then enlists the help of Ben, Gwen and Kevin to try to take Vilgaxia back. During the battle, Ben lets Zs'Skayr enter his body, returning the Ectonurite DNA to the Codon Stream. Ben transforms into Ghostfreak but the alien soon takes control of him and soon he tries to possess Vilgax, but is defeated by the light of Vilgax's sword and Ben changes back. He is now back in the Omnitrix. He also appears in the Vilgax Attacks Video Game as the Boss of his Home planet Anur Phetos.

Ben 10

 * Ghostfreaked Out (first appearance)
 * The Return
 * Be Afraid of the Dark

Ben 10: Alien Force

 * Ghost Town (first re-appearance)
 * Primus (flashback)

Ben 10: Protector of Earth
Zs'Skayr appears as the main antagonist in the Midwest. He frees Vilgax from the Null Void and teams up with him to get revenge on Ben. He also possesses Hex and tries to use his powers to bring an army of his minions from the Anur Realm, but is stopped by Ben. He leaves Hex and then attacks Ben at Chicago. Ben manages to defeat him and then sends him into the Null Void with the help of Grandpa Max.

Ben 10 Alien Force: Vilgax Attacks
After Max sent the team to Anur Phaetos to retrieve the Energy core hidden there the group quickly discovers that Anur Phaetos isn't a planet in the technical sense but in fact a type of Alternate Dimension. Verdona Tennyson arrives and uses her powers to send the group to Anur Phaetos, accidentally splitting them up in the process.

Once there Ben is lured into a fight with Zs'Skayr who is revealed to be alive, in a sense. This doesn't stop Ben from defeating Zs'Skayr using his one weakness light, afterwards Professor Paradox arrives and gets the group out of Anur Phaetos.

Ben 10: Galactic Racing
He is a playable character in the game.

Trivia

 * Zs'Skayr's name is a corruption of the word "scare".
 * In both Ben 10 and Ben 10: Alien Force no one called him Zs'Skayr - they only call him Ghostfreak.
 * In Vilgax Attacks, Zs'Skayr implies that he is undead ("Alive? Interesting word choice.", "Ben 10, as I live and breathe... not!").