Slix Vigma is an alien robot that goes around capturing aliens around the galaxy forcing them to fight for their lives on the arena of his Megacruiser ship for his audience to watch them.He first appeared in Grudge Match.
Background
Prior to Grudge Match, Slix Vigma was created by unknown workers for the sole purpose of being an announcer on a battle arena. He founded the Megacruiser and per his creators' orders, he uses it to capture random aliens using them as wrestling tools on the center of his arena. At some point, he managed to capture an entire clan of wrestlers including Technorg and Bug-Lite.
Original Series
Slix Vigma first appeared in Grudge Match, where he captures Ben Tennyson and Kevin Levin after observing them fight on Earth. After having each of them fight a Megacruiser robot singlehandly on the arena in front of the crowd and the Tetramand Prisoner, he transports to their cell with the rest of the gladiators where the guards forcibly attach shock collars to them. When Ben almost gets in a fight with Technorg, he transports Ben and Kevin to his chamber where he introduces himself to the duo and explains how he can control and see everything on the ship and that he is their guardian while on the Megacruiser. He then forcibly attaches binding shackles to their legs that will ensure suffering to each of them whenever the other feels it. They are then transported back to the arena for next battle against Technorg, where Ben teaches Kevin how to master his combined powers to put Technorg into submission. Slix orders Ben and Kevin to kill Technorg and even though Kevin did not hesitate to do so, Ben stopped him. When the prisoners plan on escaping the Megacruiser, Slix tries to stop them by preparing his ship to be blasted into another galaxy and even attempted to execute Technorg. However, Ben as Upgrade merges with Slix using him to save Technorg and unlock the escape pods enabling all prisoners to escape. When the Omnitrix timed out, Slix got angry and wanted to kill Ben for that, leading to Kevin ultimately destroying him.
Omniverse
Slix Vigma reappears in "No Honor Among Bros" as the announcer of the Golden Fist Tournament. His personality has become more excitable like a stereotypical sports announcer.