Sylth Vester is the future descendant of Sylvester. Similar to Queen Grannicus and The Royal Tweetums, he is also a native of Planet Blanc (as seen in the episode Fall of Blanc).
He was voiced by the late Joe Alaskey.
Sylth Vester wears a large suit of cyborg body armor, which covers various injuries inflicted by his previous encounters with Tweetums. He has scars from his attempts to catch The Royal Tweetums. Among his known injuries are:
- His back teeth being pulled out.
- A lack of fur on his belly from being dipped in molecular acid.
- An injured arm from getting stuck in a particle accelerator.
- A severely disfigured face from being sucked into a black hole.
He works for Queen Grannicus in her plot to prevent The Royal Tweetums from reclaiming the throne. Both were defeated in the end.
When Optimatus invaded Blanc, the Loonatics freed Sylth Vester so he could help them find Tweetums. He also helped them stopping Optimatus and Deuce's plan to rule the universe, although in the end, he was arrested by Tweetums, for telling Deuce how to use the scepter. Sylth Vester is a forceful and fierce warrior, and is practically unstoppable in hand-to-hand combat, plus, he's not really a bad guy, since he helped the Loonatics saving the universe, which can indicate that he's also able to do good. He some times says "Sufferin Succotash" just like like Sylvester. He also acts like him. He talk's like Sylvester and says some things that Sylvester is known to say.
- Aside from his ancestor, Sylth Vester is also based off of legendary Star Wars villain Darth Vader.