Zs'Skayr has an upside down, skull-like head with one eye, and his second skin modified to look like the hood and cloak of a stereotypical Grim Reaper. The facet joints on his back are larger and more curved, the skin on his arms now hangs down, much like sleeves, he also has sharp claw like nails and sharp teeth, as well as striped tentacles on his chest.
Zs'Skayr has a twisted, arrogant, power-hungry and sadistic personality. Anyone whom he considers as inferior is either tormented for his amusement or is manipulated and later destroyed once his/her usefulness has ended.
Zs'Skayr is shown to be a careful and brilliant master planner, able to come up with highly resourceful, cunning and complex schemes and plans, through which he aims to gain immense power for himself and domination over entire worlds. While Zs'Skayr tends to do most of the work by himself, he does usually recruit and utilize minions and allies. Zs'Skayr's minions aren't much more of an exception to his cruelty than his enemies; he has been known to quickly and almost happily resort to violent shows of power and intimidation (often via his possession ability) against other villains to cow them into allying with him when they're uncooperative, and he also shows little respect for his minions and tends towards flashes of abuse and threats when they don't obey him without question.
Zs'Skayr is also highly vindictive and vengeful, a side of him which is especially heightened through his vicious and bloodthirsty personality: his obsession with possessing Ben, besides becoming whole through access to the Omnitrix, is rooted in his spite over his original entrapment in the Omnitrix and his desire to make Ben feel the same way.
By human standards, Zs'Skayr can be described as matching the textbook definition of a psychopath, with notable traits being his obsessive behavior, his lack of remorse, his immense sadism, and his enjoyment of the suffering of others.
- Ghostly Powers- The atoms that make up Zs'Skayr's body are spread very thin, and thanks to the ectoplasm holding them together, Zs'Skayr can manipulate his own physical density, giving him the abilities of flight, intangibility, and invisibility.
- Psychic Abilities- Zs'Skayr can also spread his ectoplasmic reach to separate entities, living or not, adding telepathy and mental overshadowing to their capabilities.
- Heat and Light- A drawback of density shifting is that if Zs'Skayr body temperature increases, then his atomic vibration speeds up, causing his atoms to spread too thin and his physical form to completely dissipate.
- Second Skin- Zs'Skayr's second skin inhibits many of his powers, but removing it makes him vulnerable to light.
With his people following his lead, Zs'Skyar and the Ectonurites migrated from planet to planet, seeking to take control of the populace. With Zs'Skayr wanting to spread his influence too quickly, he left in search of a powerful host to aid in his conquer of Anur.
He learned about the Omnitrix from the data files of one of Vilgax's data probes, which crash-landed on his planet. He left his planet using the probe and searched the galaxy by possessing many beings. Not long afterward, he encountered Azmuth's assistant, Myaxx, while she was collecting samples with the Omnitrix on Flors Verdance.
Zs'Skayr possessed the Florauna that was being sampled, thereby adding Ectonurite DNA to the Omnitrix as well as Florauna DNA. Since an Ectonurite's consciousness exists even in a single strand of DNA, Zs'Skayr had effectively copied himself into the device. However, his personality remained dormant within the Omnitrix's DNA database for a long time. It is unknown what happened to Zs'Skayr's original form, although it is likely that either he died or his consciousness was transported inside the clone body.