Zs'Skayr

Zs'Skayr (pronounced Zis-kay) was the Ectonurite High Ecto-Lord of Anur Phaetos.

History
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, Zs'Skayr possessed the Florauna, Myaxx was sampling and thus Myaxx then got a Ectonurite-Flouarana hybrid sample. Zs'Skayr's personality lay dormant within the Codon Stream, as Ectonurites' personalities are tied to their DNA. the real zs'skayr has died somewhere between then and the original series.

Original series
He finally manages to force his way out of the Omnitrix in the episode Ghostfreaked Out After peeling off the protective layer of skin that normally covers him, he tries to take over Ben's body in order to become whole again. After a failed attempt to possess Ben, he coerces Acid Breath, Thumbskull, and Frightwig to help him by taking over Thumbskull and tossing him about the room in a show of force. He is defeated when he is exposed to sunlight by Ben at the end of the episode, causing him to burst into flames. Following this, Ben never uses the form.

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. Gathering a group of horror-themed aliens as minions, Vicktor enacted a plan to resurrect Zs'Skayr, whose master plan was to plunge the Earth into darkness. 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 Vicktor accidentally rammed Max into the projector during a dogfight. In the end, Ghostfreak is killed on board a space shuttle, when Max opens 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.

Alien Force
Zs'Skayr appears in the Ben 10: Alien Force episode Ghost Town. After being removed from the Codon Stream, Zs'Skayr has apparently been imprisoned by the Galvans. Vilgax frees him on the condition that he help defeat Ben, but Zs'Skayr betrays him and takes over Vilgax's home planet of Vilgaxia, possessing the citizens and turning them into Ghostfreak Minions. 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. Ghostfreak then tried taking over Ben's body, but was defeated by Vilgax. He is now available in the Omnitrix's selection again.

Trivia

 * The Zs'Skayr that has appeared so far in the storyline is not the true Zs'Skayr, but simply a genetic copy. It is unknown what has happened to the original Zs'Skayr. It is possible that he just passed away while trapped in the codon stream.