Malefactor

Malefactor is the fifteenth episode of Ben 10: Omniverse.

Plot
The episode starts with Ben and Rook walking to the Olde Bellwood Days festival, having been called by Natalie Alvarez for a special appearance. To Ben's dismay, his role is being dunked in a dunk tank for charity, a role that Rook immediately begins working on. As Ben fumes, the festival is suddenly attacked by Khyber's pet, in the form of Buglizard.

Ben sends Rook to find Khyber while he battles the monster, but he soon finds himself forced to save the festival-goers from the giant wooden bell at the center of the festival. Ben attempts to transform into Humongosaur but he transforms into Heatblast instead and he successfully stops the bell shortly before it crushes a boy who had previously dunked Ben repeatedly - unfortunately, Khyber's pet knocks the bell in a different direction after transforming into Crabdozer. As Rook finds Khyber and engages him in battle, Heatblast transforms back into normal and Ben transforms into Armodrillo to match Crabdozer's power, only for Crabdozer to transform into Slamworm. Armodrillo radios Rook through his Omnitrix, telling him to occupy Khyber before he can make the pet transform again, only for the rookie to report that the hunter isn't whistling to control his pet's transformations.

Deciding to try a new tactic, Armodrillo slams the Omnitrix and transforms into Big Chill, noting that he's never used it against the Khyber's Pet before. Unfortunately, Khyber's pet as Slamworm quickly transforms into a Psycholeopterran named Hypnotick, a rare and almost extinct predator of the Necrofriggians. Narrowly resisting the alien bug's first attempt to mesmerize him, Big Chill remembers the first time he saw one.

In the flashback, 11 year old Ben accompanies Gwen and Grandpa Max to Mt. Rushmore for a surprise. Once they arrive there through use of the Rustbucket, Max gives them special glasses and shows them an injured Psycholeopterran, saved by Plumbers from smugglers. After taking off his glasses to taunt Gwen, Ben accidentally gets hypnotized by the predator - luckily, the containment field prevents him from being devoured.

Suddenly, the Plumber base alarm goes off which prompts Max to investigate. Against his instructions, Ben and Gwen head out as well, finding Malware on the warpath. Ben turns into XLR8 to keep Malware busy while Gwen saves the Plumbers from danger. Unfortunately, the Omnitrix times out just as Malware gets a bead on Ben. Seeing his nephew in danger, Max attacks Malware with a Tachyon Cannon, which disrupts his structure and blows him to pieces.

However, Malware regenerates and absorbs the Tachyon Cannon, mutating into a monstrous reptilian form. He attempts to blast Max with his new weapon - which Max claims will kill every human in a 100-mile radius - but the ray is blocked by Ben when he transforms into Feedback. As Feedback engages Malware, Khyber sneaks into the Psycholeopterran's chamber to sample its DNA. Malware suddenly breaks off his battle, telling Ben that he already got what he came for. As the villain flees, Max realizes that he was after the Psycholeopterran, but the heroes find the creature as it is.

Back in the present, Big Chill tries to escape from Hypnotick, throwing off the Psycholeopterran's hypnosis by remembering that being a hero is about putting others before yourself, not being admired. He transforms back into normal, but his attacker seems reluctant to land a killing blow, leading Ben to realize that Khyber and his dog are just wasting his time. Meanwhile, Rook has come to the same conclusion, with Khyber hinting that his ally has come for the Proto-TRUK.

Acting on Rook's information, Ben transforms into Heatblast again in order to reach the truck, only to come face to face with Malware himself. As the villain threatens him and flees, Ben leaves Rook to check the Proto-TRUK for stolen items before pursuing Malware. He transforms into Humungousaur, but Malware sends a gas tanker towards a school bus - while Humungousaur goes to save the bus, Malware escapes. Back at the Proto-TRUK, Rook reveals that the TRUK's memory core was destroyed, along with the auxiliary power systems. He asks Ben about Malware, but they are interrupted by one of the boys from the festival, who thanks Ben for saving his life.

After transforming Humungousaur again in order to pick up the wooden bell and return it back into its place, Ben transforms back into normal and resumes his charity duties, encouraging spectators to come and dunk Four Arms. Much to his dismay, the only comer is Rook, with an entire bucketful of balls.

Major Events

 * Mt. Rushmore makes its first appearance as an active Plumber base.
 * It is revealed how Malware got into his current form.
 * Ben encounters and fights Malware for the first time in 5 years.

Omnitrix Alien Debuts

 * Brainstorm (Omniverse debut)

Nemetrix Alien Debuts

 * Hypnotick (first appearance)

Minor Events

 * This is the first episode in which Zed was able to switch forms without Khyber whistling for her to do so.

Present Characters

 * Ben Tennyson
 * Rook Blonko
 * Natalie Alvarez (first appearance)
 * Madison (cameo)
 * Mr. Baumann (dream; cameo)
 * Pakmar (dream; cameo)
 * Julius (cameo)

Past Characters

 * Ben Tennyson (11 years old)
 * Gwen Tennyson (11 years old)
 * Max Tennyson (61 years old)
 * Plumbers
 * Jerry
 * Molly Gunther
 * Zorian (first appearance)
 * Smuggled Psycholeopterran (first appearance)

Present Villains

 * Khyber
 * Khyber's Dog
 * Malware

Past Villains

 * Khyber
 * Malware

By 16 year old Ben

 * Brainstorm (first re-appearance)
 * Stinkfly (cameo)
 * Wildmutt (cameo)
 * Spidermonkey (cameo)
 * Humungousaur (x3; third time was cameo)
 * Heatblast (x2; first time intended alien was Humungousaur)
 * Armodrillo
 * Big Chill

By 11 year old Ben

 * XLR8
 * Feedback

By Zed

 * Buglizard
 * Crabdozer
 * Slamworm
 * Hypnotick (first appearance)

Allusions

 * One of the Plumbers had a visor like Cyclops from X-Men.
 * The Tachyon Cannon appears after being referenced in Ultimate Aggregor.
 * Heatblast shouts his name in this episode, like in Ultimate Alien and Humungousaur and Big Chill in Of Predators and Prey: Part 2.
 * The logo for the Dunk Ben 10 game at the Olde Bellwood Fair is stylized like the original series logo.

Trivia

 * It's explained how Bellwood was founded, and that it was named after wooden bells.
 * In the flashback, Malware's cannon is on his left hand, while in the present, it's on his right.
 * This is because Malware is able to switch which hand he's using the gun for.