Vilgax has beaten the heroes of 10 planets and taken their powers as his own. He has now returned to Earth and issued a conquerer's challenge to Ben where the victor claims dominion over the Earth. In trying to beef up the Omnitrix for his battle, Ben overloads the watch, loses four of his transformations, and turns Kevin into a monster.

Vilgax has beaten the heroes of 10 planets and taken their powers as his own. He has now returned to Earth and issued a conquerer's challenge to Ben where the victor claims dominion over the Earth. In trying to beef up the Omnitrix for his battle, Ben overloads the watch, loses four of his transformations, and turns Kevin into a monster.

Ben, Kevin, and Gwen look into a disturbance that has brought Pyroxivores to the surface from the underground. During their search, they meet a riley creature named Mouldywarp who is angry at a “claim jumper” that has moved in on his ground and is scaring his Pyroxivores. They soon discover that Vulkanus is causing the disturbances with his plans to drill to the center of the Earth

Every 15 years, a group of aliens travel to a remote farm town to participate in their Popcorn Festival. They aliens enjoy the popcorn while the farmers enjoy the rewards of cleaning up after. However, when one of the aliens goes missing, his best friend calls upon the services of Ben to help find him before the week is over and the aliens must return home.

Ben receives a holo-viewer message from an alien named Probity. Her home world is ravaged by a war that has lasted for decades and she asks Ben to help solve the conflict. Ben, Kevin, and Gwen travel to her world and try to end the unnecessary fighting. Simple, right?

Octagon and Rhomboid Vreedle are repo men who have been hired to return Ship to the Upgrade who spawned him. Ben and Kevin fly through space to convince the judge to rescend his order while Julie and Gwen try to hold off the trigger happy Vreedles from taking Ship. In trying to protect Ship, Julie discovers that the best way to protect him is with his help.

Ben is running away from a bounty hunter named Sunder who is after Ben and the Omnitrix. Sunder catches Ben but, in trying to remove the Omnitrix, sends Ben to the Null Void leaving only his left hand on Earth. Julie discovers his single hand and must find a way to bring Ben back from the Null Void while keeping his hand safe from the persistent and lethal bounty hunter.

A series of earthquakes awakens a Highbreed officer who had been hibernating deep under the Earth's surface. He believes that the Highbreed have lost the war and activates a failsafe device that is programmed to destroy. Ben must now work together with Kevin and Gwen, not only to save Grandpa Max, but also the world from this “giant” problem.

Kevin is beginning to lose all hope that he might one day return to being normal when he is charmed by a beautiful girl that seems to understand. Kevin finds himself under her spell (literally) as Charmcaster has returned and is forcing Kevin to do her biding. Kevin has no choice but to obey his master and to destroy Ben and Gwen.

Vilgax visits the prison that holds Ghostfreak prisoner. He gets more than he bargained for, though, when Ghostfreak begins possessing the citizens of Vilgaxia and amassing an army. Vilgax must but his pride aside and work with Ben to keep Ghostfreak from carrying out his ghastly plans.

Ben's foe, Darkstar, convinces Kevin to join him in a quest to retrieve an ancient artifact called the Dominus Librium rumored to have the ability to help them both escape their current degenerate states. They succeed in obtaining it and use it to return themselves to their former states only to find it has stripped them both entirely of their powers.

Kevin, Ben, and Gwen find a curious alien box in an alley that has the ability to turn into a robot version of whatever it sees. This spells trouble for our heroes when the Vreedle brothers show up and try to take it by force. The robot becomes very dangerous and Ben must stop the Vreedle brothers from capturing the device while also trying to keep the device from blowing up downtown Bellwood!

Zaw-Veenull, a Luodan ambassador, asks Ben to deliver their crown prince, Tiffin, to Jarrett in order to keep peace between the two species. Shortly after they begin their trek in space, the Omnitrix malfunctions and turns Ben into an Appoplexian named Rath who wants to fight anything that breaths.

In the middle of fighting another Techadon robot, Ben, Kevin, and Gwen are unexpectedly transported by the Omnitrix to an alien planet named Primus. They soon discover that they are not alone and that Vilgax is there to stop the Omnitrix from its source.

Despite being warned by Professor Paradox, Gwen travels back in time to prevent the accident that turned Kevin into a monster from ever happening. Gwen returns to the present only to find that her time traveling caused a series of events that led to Hex ruling the world. It's up to her to fix the future that she created.

An ill Ben is pleased to see an old friend in Tetrax but is caught off guard when Tetrax demands that Ben give him Chromastone. Ben doesn't even have a chance to explain what happened to Chromastone when Tetrax attacks him demanding that he be handed over. Ben's situation only gets worse when Vilgax shows up and it is learned he is after the same thing.

The Plumber's Helpers are called upon by Grandpa Max to rescue him from an abandoned space station where he is being attacked by….Ben! The team must now find a way to work together as they try to save Max, stop Ben, and keep the space station from crashing into the Earth!

One day when Kevin returns home to find his house ransacked, he enlists Ben and Gwen's help to find out who did it and why. They soon cross paths with Ragnarok, a deadly criminal who recently broke free from the Null Void and is in search of a special key. Kevin is intent on stopping Ragnarok from obtaining the key, especially after he learns the truth about Ragnarok and his father.

Albedo Ben has stolen the Ultimatrix (an upgrade to the Omnitrix) from Azmuth and has used it to kidnap Gwen and Kevin. Ben goes to face Albedo Ben and rescue his friends when he quickly discovers that Albedo Ben has been working in conjunction with Vilgax. Ben is defeated by the pair and gives up the Omnitrix to save himself and his friends.

Albedo Ben has stolen the Ultimatrix (an upgrade to the Omnitrix) from Azmuth and has used it to kidnap Gwen and Kevin. Ben goes to face Albedo Ben and rescue his friends when he quickly discovers that Albedo Ben has been working in conjunction with Vilgax. Ben is defeated by the pair and gives up the Omnitrix to save himself and his friends.