|“||Ben 10, I've come to kill you and conquer your world. Is now a bad time?||”|
–Vilgax to Ben
Vilgax is the main antagonist during the first series of Ben 10 and the third season of Ben 10: Alien Force, and the arch nemesis of Ben Tennyson. Vilgax is an incredibly powerful alien tyrant who wants the power of the Omnitrix to power his armies so that he can conquer the galaxy.
In the wake of the Fusion invasion, Vilgax has temporarily put aside his differences with Ben, and has joined forces to counter the alien threat. Despite the danger from Planet Fusion, however, Vilgax has his own secret agenda. He constantly sends the hero on missions to recover items, but refuses to tell their purpose.
Aware of his hostility towards Mojo Jojo and Mandark, Fusion Ben tricked Vilgax into engaging the two villains in the Spaceport infected zone. The hero was able to break up the fight, and sent Vilgax packing.
During the crisis of Planetoid Fusion, Vilgax sabotaged both Dexter's and Mandark's cannons so that they would hit Planet Fusion instead of the Planetoid. Vilgax hoped that he could harvest the technology aboard the Planetoid for his own benefit. His plan was foiled, however, when Courage reversed the polarities on a UFO magnet pulling the planetoid towards earth. As a result, the Planetoid was crushed. Enraged, Vilgax followed the hero into Fusion Juniper Lee's Secret Lair to destroy him/her for helping Courage find the magnet. He was once again defeated, along with Fusion Juniper Lee.
As of Febuary 2010, his attire has been changed to that of his design in Ben 10: Alien Force. He has recently been seen in the Future at Genius Grove. He requires the hero to bring him several items, including the Highbreed Teleportation Drive, which he says he will use to reactivate his ship, travel back to the past, and use what knowledge he's learned of fusion matter to deactivate Ben's Omnitrix.His ship, "The Chimerian Hammer," serves as the main location through most of the FusionFall Adventure "Alien Abduction". This area is accessible through a spell of Gwen's teletransportation from the interior of the ship. The only image of the exterior of the ship is shown in the ad of "Alien Abduction."