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.
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, 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 when Zac got the Omnitrix, and a genetic clone was created in full power.
His mind lay within the DNA sample of Ghostfreak.He finally manages to force his way out of the Omnitrix. After peeling off the protective layer of skin that normally covers him, he tries to take over Zac's body in order to become whole again. After a failed attempt to possess Zac, 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 Zac causing him to burst into flames.
Zs'Skayr is later revived by an alien scientist named Dr. Vicktor. Gathering a group of 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 Thep Khufan they set up a Corrodium beam that will block out light from the sun, allowing Zs`Skayr to exist in eternal darkness. Zs`Skayr 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.
3 years later Zs`Skayr has once again been revived somehow and is now for some reason in prison,Vilgax frees him on the condition that he tell him the secets of the Omnitrix and the knowledge to defeat Zac but Zs'Skayr betrays him and takes over Vilgax's home planet of Vilgaxia, possessing the citizens and turning them into Ectonurite Minions. Vilgax then enlists the help of Zac, Wes, Gwen and Kevin to try to take Vilgaxia back. During the battle, Zac 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 Zac changes back. Zac gains the ability to trun into Ghostfreak without Zs`Skayr`s personallty in him after this.