Vulkanus

Vulkanus is a Detrovite(the same species as Technorg) who partnered up with Sixsix in order to build a weapon capable of destroying a solar system.

Ben 10
In the original series, he is almost always seen with Sixsix. Unlike Technorg, he isn't enhanced in any way. He is stopped by Ben and the Galactic Enforcers in the episode, The Galactic Enforcers. He reappears in Ben's dream world in Perfect Day working alongside Sixsix again. In the start of the future episode Ken 10, where he was defeated by Ben 10,000 and was transported to the Null Void.

Ben 10: Alien Force
Vulkanus makes a brief appearance in Ben 10: Alien Force in the episode Kevin's Big Score. According to Vulkanus, he was betrayed by Kevin during a "counterfeit isotope" scam a few years earlier. Kevin left him holding the merchandise when The Plumbers arrived, and though he managed to escape, the Plumbers destroyed his ship. Unable to leave Earth, he resorted to trading low-level alien technology to get by. When Kevin arrives looking to obtain an important item(a holo-viewer from Grandpa Max), Vulkanus decides to get back at him for the betrayal by forcing Kevin to absorb a small piece of Taedenite, the rarest living gem in the galaxy. This causes Kevin's body to mass-produce the gem, thus giving Vulkanus an endless supply. However, he is foiled by Ben, who uses Big Chill to literally freeze off his armor, revealing that Vulkanus is really nothing more than a minuscule alien in a giant suit. Rather than attempt to arrest him, however, Kevin leaves Vulkanus with the small fortune in crystals he had managed to chip off beforehand, considering it as payment for his past actions.

He reappears in Inferno where he plans to detonate a bomb which will raise the Earth's temperature to 800 degrees.The bomb is stopped by Ben and Kevin is happy that Vulkanus wasted his money.

He makes a brief appearance in Con of Rath. When Ben(as Rath), Gwen, Kevin discover they need Taedenite to power their ship, Gwen tells Kevin that every time they come across Taedenite they run into Vulkanus. Kevin says their imagining things only to be confronted by Vulkanus. Kevin tries to negotiate with Vulkanus using a gold credit cube(an alien form of currency with no spending limit) but Vulkanus holds firm. He is defeated by Rath who ruined most of his Taedenite. Beaten Vulkanus is forced to hand over his remaining Taedenite.

Ben 10: Ultimate Alien
Vulkanus also appears as one of the villains after Ben in Hit 'Em Where They Live, teaming up with Zombozo and Charmcaster and is beaten at the end by Ben as Ultimate Big Chill. Vulkanus was suddenly afraid of Ultimate Big Chill after witnessing the effect with his "ice flames".

Vulkanus is going to appear in Ben 10 Ultimate Alien: Cosmic Destruction, evidenced as his pick-axe minions, and himself, are seen in a few of the screen shots.

Ben 10

 * The Galactic Enforcers(first appearance)
 * Perfect Day(dream)
 * Ken 10(non-canon)

Ben 10: Alien Force

 * Kevin's Big Score
 * Inferno
 * Con of Rath

Ben 10: Ultimate Alien

 * Hit 'Em Where They Live

Trivia

 * Vulkanus has been beaten by Ben as Big Chill two times, once as normal Big Chill, and the other by Ultimate Big Chill.
 * His name probably derives from "volcanic", due to his heat resistant armor, and the name of his home planet, Vulcan, which, in itself, is named after the Roman god of smithery of the same name.
 * In the original series, Vulkanus seemed to be at the same build as Technorg minus the mace hand, but from Alien Force onward, he is shown to have a infant-like body. Dwayne McDuffie has confirmed that he was this size the whole time his suit was merely colored in mimic flesh