In the middle of fight with a Techadon robot, Lodestar, Gwen and Kevin are unexpectedly transported by the Omnitrix to a planet named Primus. They soon discover that they are not alone and that Vilgax is there to take the Omnitrix's power straight from its source.
After being attacked by various blue alien wasps (during which the Omnitrix detaches itself from Ben), Ben, Gwen and Kevin find Vilgax fighting Humungousaur, who turns out to be Azmuth. After turning into Rath, Azmuth is defeated by Vilgax.
After capturing Ben, Gwen and Kevin, Vilgax takes the Omnitrix, but can't figure out how to use it. Ben explains it to him, turns him into Goop, and turns off his Anti-Gravity Projector, leaving Vilgax powerless. Ben takes the Omnitrix off him, which immediately turns him back. Ben turns into Cannonbolt and kicks Vilgax into the Codon Stream. Vilgax then absorbs the power from the Codon Stream, which dramatically increases his size and strength. Ben turns into Way Big and, after a short fight, tosses Vilgax into outer space. After rethinking his position, Azmuth allows Ben to keep the Omnitrix.
Kevin: I got this! (jumps in after Ben) Gwen: (panicking after a while) Ben! Kevin! (uses her mana to burst them out) Kevin: (after landing on a tree with Ben) What part of "I got this" do you not understand?
Ben: Azmuth. Everything's going to be okay. Azmuth: Did you just "there, there" me?
Kevin: (after Ben defeated Vilgax, following Azmuth, and speaking to Gwen about the incident when Ben gave in with Vilgax) Couldn't you have acted way over the top when Ben gave in to Vilgax? (pretends to act like Gwen, putting up a girly voice) Ben, noooooooooooo!!! Gwen: (defending herself) I was just trying to help Ben trick Vilgax! Kevin: Sure. Keep telling yourself that! (Gwen gave Kevin an angry look)
Vilgax: (after seeing Azmuth with Ben, Gwen and Kevin, trying to figure out the secrets of the Omnitrix) This world is important to you, eh, Azmuth? More important than your own life? Or those of these children? That leaves me an intriguing option. Tell me how to activate the Omnitrix, or I'll destroy the whole planet. Ben: No! Azmuth: Ben! Ben: Azmuth can't help you. He's just trying to protect me. I'm the only one who knows how to work the watch! Azmuth: That's not- Kevin: Button it, genius.
Vilgax: You'll work the Omnitrix for me? Ben: (thinking of an agreement) If you let my friends go! Vilgax: We have an agreement! You teach me to operate the Omnitrix, and I'll free your friends! But you, Ben Tennyson, will die. Ben: (thinking of something else in mind, putting up an act) All right. I guess I have no choice! Gwen: Ben, noooooooooooo!!!!! Ben: (shouts to Gwen) I know what I am doing Gwen! Kevin: Since when? Vilgax: (breaks Ben's chain and throws him) Show me, human! Ben: (starting to teach Vilgax, as much to Kevin's, Gwen's and Azmuth's shock) See, when you turn the dial, you have to be pushing in at the same time. (stops at the hologram of Goop and presses it) Azmuth: (closes his eyes since the light of the Omnitrix is too strong) Ben, noooooo!!!!! Vilgax as Goop: (does some experimenting with Goop's power) The power is unbelievable! I can do anything! Ben: Almost anything! (snatches Goop's gravity projector and deactivates it, double-crossing Vilgax) Vilgaxas Goop: (tries to attack Ben, but falls to the ground before he can) What did you do? (straining to get up) I can't move! Ben: (cunningly) I know. I turned off Goop's artificial gravity! (snatches the Omnitrix from Vilgax and puts it on his hand, now trying to show off) Who's the hero? Gwen and Azmuth: (together and annoyed by Ben's act) You are. Ben: Everybody? Kevin: (also annoyed and rolling his eyes) You are. Ben All I ask for is a little credit.
Ben: Azmuth! Kevin: Quick! Chew through our chains! Azmuth: I am not a rodent! Kevin : Could've fooled me...
Way Big: (grabs Vilgax's hand, whacking his face repeatedly with it) Stop hitting yourself, stop hitting yourself, stop hitting yourself! Kevin: Heh heh heh heh! Classic.
Ben: So are we okay again? I mean, does this make up for- Azmuth: Damaging my Omnitrix? No. I shouldn't even allow you to leave with it. Ben: But will you? Azmuth: You are welcome, Ben Tennyson.
Azmuth: Give me a minute... I'm a little out of practice... Ben: It's Azmuth! Gwen: We should've known! The Omnitrix kept saying it was looking for its creator! (Vilgax throws a boulder at Azmuth, who transforms into Rath and catches it) Azmuth(as Rath): Let me tell you something, Vilgax, conqueror of ten worlds! Azmuth will defeat you! Azmuth will hunt you down even though you're standing right here! You are no match for the awesomeness of Azmuth!
Naming and Translations
While here, Humungousaur (Azmuth) and Vilgax are en par in strength, in Vengeance of Vilgax: Part 2, Vilgax beats Ben as Humungousaur, even in his giant form.
Although it is shown that Azmuth does not intend to forgive Ben, he allows him to keep the Omnitrix, but cannot trust him anymore.
When Vilgax changes into Goop, he still talks in his own voice.
When the Omnitrix came off of Ben and went onto Azmuth, Azmuth turned into Humungousaur, with the same appearance as Ben as Humungousaur, yet when Vilgax put on the Omnitrix and turned into Goop, he looked a little different than Ben as Goop.