The Mother of All Vreedles
With his secret identity now revealed to the world, Ben Tennyson continues to fight evil as a superhero with the help of the newly acquired Ultimatrix.
A mysterious alien girl named Eunice has no memory and is being hunted by Sunder. While evading Sunder, Ben soon discovers that Eunice has nature-based abilities.
Ben, Julie and the rest of the heroic crew embark on a dangerous journey that could cost them all their lives in an effort to achieve the safe return of Ship and his former owner Baz-L.
In an ancient castle, in a scientific lab, an old hag tells her master, a prince, tells him to not unleash an ancient power they have taken. The hag tries to tell Prince Gyula to go the peaceful way, but the prince and his father, the king, want to see this power, but it is revealed to be the frozen body of Dr. Vicktor. The prince thinks of freeing Dr. Vicktor of his icy prison to help them against the rebels in their civil war, but the king tries to persuade his son to not release him. Meanwhile, the gang is flying through the forest in Kevin's jet, in order to help the king of Zarcovia to help them against the rebels in the civil war. When they are attacked by some missiles, Ben tries to become Jetray, but becomes Echo Echo instead. When the missiles are flying at the jet, Ben becomes Ultimate Echo Echo and destroys the rest of the missiles. However, they are attacked by the prince and their soldiers, but the king stops them. The king explains that the prince changed ever since his mother's passing, and blames his father for his mother's death. In order to get past the security that goes to Dr. Vicktor's chamber, Ben uses Big Chill to become intangible through the lasers and shut them down. When they find Dr. Vicktor's corpse, they are found by the soldiers and commence fighting them. However, Dr. Vicktor's ice block begins to melt, and Ben is trying his best to keep him frozen, but Dr. Vicktor breaks free, alive and well.
Jimmy Jones is looking for the biggest new story he and Ben can tackle, but thats when he stumbles upon a strange pink tentacled creature which crashed from the sky into a near by cave.
Gwen is excited by the prospect of her cousin Sunny paying the team a visit while dealing with the Robots of Dimension 12. But her excitement quickly turns into trepidation when it is uncovered that her cousin is not all that she appears and has some particularly sinister intentions.
Victor Validus resurfaces and attacks Ben at night. Elena Validus and the nanochips return.
The Forever Knights unleash an evil force mistaken for an ancient weapon.
Ben, Gwen, and Kevin are summoned to a Plumbers' Academy to go under training that is supervised by Magister Hulka.
Gwen has always been a multi-tasker, trying to juggle school, hobbies, friends and her work as a hero, waking up early and going to sleep late. But Gwen's already packed day is about to get worse when Dr. Animo attacks with an army of giant frogs and Gwen is forced to make a hard choice.
Following a visit from Paradox after a fight with Eon, Ben 10,000 arrives 20 years from the future to seek the aid of his past counterpart in tracking down Eon.
The history of Max and Verdona Tennyson in flashbacks.
The secrets of Area 51 are revealed to Ben Tennyson by Colonel Rosum after Old George infiltrates Area 51. (ChamAilen and Ultimate Wildmutt first appears in this episode).
With the help of The Forever Knights, Old George starts a war against all aliens on Earth.
A Xenocyte queen invades the Arachnachimps' planet.
Techadon robots go after Ben on orders from Vulkanus
Julie joins a cult that worships Vilgax
Albedo profits from Ben's fame
The Perfect Girlfriend
The ultimate aliens inside Ben's Ultimatrix demand their freedom!
The gang looks into the Pacific Garbage Vortex at the request of the government.
The Vreedle Brothers need help dealing with their mom.
Vilgax steals Old George's sword and attempts to gain Dragon's powers.
Azmuth reveals how Old George got his sword and slayed Diagon.
A mysterious weapon master from Techadon visits Earth and wants the Ultimatrix.
Gwenand the gang revisit Legerdomain in hopes of rescuing Charmcaster.
Charmcaster and Darkstar team up to destroy Ben, Gwen and Kevin.
Jennifer Nocturne is recaptured by Captain Nemesis aka Overlord.
Dr. Animo returns with a plot to transform eggs into pterodactyls.
Albedo attempts to get even with Ben, by trapping him in a dream version of Bellwood, and dispatching an assortment of villains, as well as versions of Gwen and Kevin desiring the Ultimatrix, to attempt to defeat him.
The Forever Knights battle Diagon's Esoterica, and Ben's plan to help the knights fails.
Ben, Gwen, Kevin, and George trash Diagon's City while battling a reborn, Lucubra-morphed, power hungry Vilgax. Diagon is released and plans to become ruler of Ben's Universe.
Ben's fight with Vilgax and the Dagon continues in this final episode.