Zs'Skayr's Minions are people or aliens who have worked for Zs'Skayr.
The Yenaldooshi was sent by Doctor Viktor to steal communication equipment from a reservation that Ben, Gwen, and Grandpa Max were visiting in Benwolf. Ben first fights against the Yenaldooshi as Wildvine. When Ben is transformed back to his normal self by the Omnitrix, the Yenaldooshi slashes the Omnitrix, causing the device to scan its DNA (signified by its face turning yellow) and gradually change Ben into Blitzwolfer.
In its next battle against Cannonbolt, the Yenaldooshi appears to be caught in a cave-in. The device that it was building is shown coming online at episode's end, its purpose left unrevealed.
In the next episode, Be Afraid of the Dark, the Yenaldooshi's transmitter explodes when Grandpa Max rams a space shuttle into Ghostfreak's Corrodium Projector, destroying it. It is unknown if the Yenaldooshi survived the explosion.
The Mummy was sent by Doctor Viktor to find a dangerous element called Corrodium, that is theorized to have crashed on Earth a few thousand years ago. Grandpa Max explains that the crystals are a potent but unstable power source, and the radiation emitted by the crystals causes almost instant mutation in humans and other Earth-born creatures.
Todd Maplewood, a boy Ben and Gwen met, said it arrived in purple lightning, which is the same way the Yenaldooshi arrived in Benwolf. Max states there may be a connection between the Yenaldooshi and the Mummy, which is proven correct in The Return.
During Ben's battle with the Mummy, its DNA is scanned by the Omnitrix, giving Ben access to Snare-oh. The Mummy is frozen solid by Upgrade and buried, along with its Corrodium, under a thick bed of concrete.
It was dug up by the Yenaldooshi in The Return and assists in Dr. Viktor's plan to plunge the Earth into eternal darkness.
When Frankenstrike is fighting Zs'Skayr and the Mummy in Be Afraid of the Dark, Dr. Viktor inadvertently sends both himself and the Mummy to the Null Void through an ill-timed use of his teleportation device.
The Mummy has not been seen since.
Dr. Viktor (formerly)
Dr. Viktor worked at NASA, disguised as a human scientist as a means to hijack a space shuttle. His immediate plan was to resurrect his master, whose ultimate plan was to prevent the sun's light from reaching Earth using various satellites (therefore meaning that Zs'Skayr would be at full power all the time). Dr. Viktor was not treated with respect after Zs'Skayr is resurrected. After he asks why they need Ben, Zs'Skayr takes control of his body and throws him around.
Dr. Viktor served as the leader of the three horror-themed aliens when Zs'Skayr was not present. The purple lightning that the previous two horror aliens appeared in was generated by a teleportation machine that he used.
Dr. Viktor's first appearance was in The Return, where he succeeds in reviving Zs'Skayr. In the next episode, Be Afraid of the Dark, Ben fights Doctor Viktor and Zs'Skayr on Earth. Ben gains use of Frankenstrike when Viktor finds Ben and grabs him by the wrist, unintentionally allowing his DNA to be scanned by the Omnitrix. Viktor essentially defeated himself near the end of the episode: in an attempt to teleport Frankenstrike to an unspecified location, he and the Mummy were tossed into the portal he created.
Lord Transyl (formerly)
Lord Transyl was resurrected by Zs'Skayr in The Vampire Strikes Back. Though he initially responded by attacking him and his minions, Zs'Skayr got a hold of him by possessing his body and convinced him to cooperate. Lord Transyl managed to enslave the entire population of Anur Transyl with his Corruptura, and his DNA was scanned by the Omnitrix which created Whampire. Zs'Skayr planned on using Lord Transyl's DNA to resurrect the rest of the Vladat race, but both were defeated by Dr. Viktor betraying his master due to his hatred for the Vladats.
Kuphulu was another henchman of Zs'Skayr. He made his debut in Rad Monster Party where he picked of Ben's team members one by one. He was ultimately defeated by Crashhopper. In Charmed, I'm Sure he was seen in Zs'Castle Zs'Skayr working on the resurrection machine. In The Vampire Strikes Back, Kuphulu, along with fellow members Crüjo and Viktor were controlled by Ben's Corruptura to aid in the fight against Lord Transyl.
Crüjo was another henchman of Zs'Skayr. He made his debut in Rad Monster Party where he was seen being reunited with his boss. Later, he fought Ben's team. In Charmed, I'm Sure he was seen in the Zs'Castle Zs'Skayr. In The Vampire Strikes Back, Crüjo, along with fellow members Kuphulu and Viktor were controlled by Whampire's Corruptura to aid in the fight against Lord Transyl.
Circus Freak Trio (formerly)When Zs'Skayr first escaped from the Omnitrix, he encountered the Circus Freaks in a school and they agreed to work for him after he persuaded them by throwing Thumbskull around the room. When the trio confronted Ben, as Four Arms, Zs'Skayr possessed the trio individually in order to fight him. When Zs'Skayr was defeated by Ben later on, the trio were arrested.
Citizens of Bellwood (formerly)
In From Hedorium to Eternity Zs'Skayr brings his people, the Ectonurites from their homeland to Earth, to get inside the bodies of the grown-ups and control them, while he plans to take over the Earth. His plans are, however, thwarted by Ben and his team as Cooper manages to sever the connection and stop the portal, sending all the Ectonurites along with Zs'Skayr back to their planet.
Enslaved Chimera Sui Generis (formerly)
They were created when Zs'Skayr possessed a Chimera Sui Generis, turning them into slaves for his hive mind. When struck hard enough, they seemed to simply vanish. They were restored back to normal after Zs'Skayr was defeated.