Ben 10: Omniverse - Season 8

This episode is a flashback to Ben and Gwen's younger days when they were eleven. Zs'Skayr returns with a plan to have his fellow Ectonurites to possess the inhabitants of Bellwood to develop a device to permanently block out the sunlight on Earth so he can colonize the planet with more Ectonurites.

Khyber teams up with a Slimebiote, a DNA-eating parasite, named Skurd so he can safely use the Nemetrix (which he stole from the plumber base earlier) to eliminate Ben. The plan backfires when Skurd discovers the vast amount of DNA he can consume from the Omnitrix and decides to latch onto it, to both Khyber and Ben's dismay. As Khyber goes mad from extended use of the Nemetrix, Skurd's merge with Ben allows for recombination of aliens mid-fight to give a combative edge, giving Rook time to remove the Nemetrix with very minimal damage to Khyber.

Exo-Skull, Subdora and Eon attack a hidden underground cavern to retrieve a rare egg of a Time Beast. Professor Paradox and Ben 10,000 teams up with Ben and Rook to stop the Time Beast. Rook, Ben and Skurd go after the Time Beast while Ben 10,000 and Professor Paradox fight Exo-Skull and Subdora. However, a series of mistakes lead the five of them to constantly travel through time to correct their actions. Eventually the time beast is captured, but at the end of the episode, Eon delivers two Time Beast eggs to Maltruant.

During Kai's search for the Temple of the Sky, she reluctantly teams up with Ben, Skurd, and Rook at the insistence of Kai's grandfather. As they search, Ben teases Kai about Spanner's telling them they are married in the future, and as he shows her more clues they show more attraction, despite Kai denying Spanner's prediction. Upon reaching the temple and finding the relic inside, the guardian of the temple is an eons old Galvan tasked with protecting a dangerous component of Maltruant by Professor Paradox. Maltruant still succeeds in gaining the second of his three lost component.

Charmcaster traps Gwen in Ledgerdomain to exact her revenge once and for all, turning her into a stone totem. When she then attempts to take over Gwen's headquarters at Friedkin University, Ben, Kevin and Rook fight back with the aid of the great sorcerer Bezel. Charmcaster is eventually defeated and turned into a totem herself, trapped in her own bag, which restores Gwen, Hex, Adwaita, and Darkstar to normal. Darkstar is arrested, Adwaita escapes, and Charmcaster is kept in Hex and Gwen's custody under the hope that she will see the error of her ways someday.

While Rook is stuck on graveyard shift at Plumber HQ, his sensei Kundo returns as a cyborg to purge the galaxy of technological influence. Ben and Max take a massive Plumber squadron to stop Yeta, a female Shockquach alien, from continuing her criminal destruction. They later find HQ on lockdown because of Kundo and try to break into the base to give Rook back up. Fistina, the only prisoner, is deputized by Rook so as to help defeat Kundo. Following Kundo's defeat, Rook is effectively promoted to Majestor and Fistina is allowed to go to the academy following her time served.

Ben finally manages to rid himself of Skurd... just when he needs the Slimebiote most. Vilgax and Albedo team up to steal Malware's calcified husk to convert into a war armor for Vilgax to defeat Ben. As Ben fights Vilgax, he realizes how much he needs Skurd to help him, while Azmuth and the Galvans (Luhley, Blukic and Driba) fight Albedo. Azmuth uses a device he made years ago which disables Albedo's Ultimatrix and frees Skurd, in time to merge with Ben and defeat Vilgax. Ben thanks Skurd for his rescue, while Luhley decides to go on a date with Driba, while having her cousin date Blukic. In space, Vilgax's stone form oozes out what appears to be a reconstituted Malware.

Ben is being forced to be in an alien reality show called the Most Delicious Show and he watches as all the girls he'd met in his life to win the reality show's games to be the new Mrs. Tennyson. Soon, Kai Green wins the reality show, with Ester later revealing that she found another boyfriend-Sunny's old sweetheart Antonio.

In an alternate future timeline, Ben 10,000 and Kai Green (at this point in time, Kai Tennyson) are at Plumbers' Headquarters having a party for Grandpa Max because he is retiring from the Plumbers and Rook is being promoted to be in charge of the Plumbers until Maltruant, Exo-Skull and Subdora secretly attacks Plumbers' Headquarters to get the Annihilaarg and the Dwarf Star for Maltruant to become more strong. Ben 10,000 and Kai Tennyson both discover that their ally Chrono Spanner is actually their own ten-year-old son, Kenneth Tennyson.

Ben and Rook follow Maltruant through the time stream. Ben has an adventure with George Washington, in 1773, fighting Maltruant and Vilgax. After defeating Vilgax, Ben and Rook chase Maltruant in the time stream to the beginning of time itself onto the starship of the Contemelia (the creators of the Annihilaarg) where Maltruant attempts to create a universe of his own using his own Anihilaarg. In a climactic battle, at the beginning of time Ben nearly dies trying to stop Maltruant from building his own universe but then it is revealed that the Omnitrix has a fail-safe to prevent its keeper from dying.

Using the combined power of all of the Omnitrix aliens', Ben absorbs the Dwarf Star-powered Anihilaarg and uses its immensely strong, destructive power to defeat Maltruant, trapping him in a time loop that will result in him reliving the same events eternally. The Contemelia then reveal the origins of Skurd, declaring the Slimebiote to be the most vital extraterrestrial being in all of creation (to Skurd's shock). As Skurd departs with his ancestors to help develop the New World, Ben and Rook look on in awe. A new dawn rises as Ben creates a universe of his own. Back on Earth, feeling bored after the incredible sight they witnessed, Ben decides to go on a road trip across the recreated universe with Rook, Gwen and Kevin.