To achieve his ultimate form centuries before the Clone Wars, Durge voluntarily underwent a cybernetic surgery to permanently merge his “body” with his armor, turning him into a more efficient and powerful killing machine. To use another X-Men analogy, this makes Durge sort of a reverse Wolverine, but this time, the adamantium is on the outside of his body instead of inside.
What Happened to Durge?
Though we can find all sorts of analogs in other franchises (X-Men, Star Trek, et al.), there aren’t a ton of prevalent non-humanoid aliens in Star Wars canon. This made Durge pretty damn unique in the 2000s. And although he was eventually killed by Anakin Skywalker in the (non-canon) Revenge of the Sith prequel comic books series Obsession — the Jedi launches the bounty hunter into a star! — Durge was almost reintroduced into the Disney canon later.
Just as Asajj Ventress was rebooted for The Clone Wars and Thrawn was re-canonized for Rebels, Druge nearly made a comeback in a revised form. At one point, The Clone Wars showrunner Dave Filoni and his team reportedly considered bringing back Durge as a human bounty hunter, but with a similar suit, and presumably, similar regenerative powers. But this was not meant to be. Durge was instead replaced by the Duros bounty hunter Cad Bane and plans to revive the old villain were completely abandoned.
But just because Durge is no longer canon doesn’t mean fans can’t work around that. There’s a way to invent your own headcanon where Durge still does play a part in the Clone Wars. Who’s to say Asajj Ventress didn’t briefly team up with Durge in an untold Disney canon Star Wars story? And maybe Obi-Wan did fight him on Muunilinst. Just because we didn’t “see” a new version of Durge in The Clone Wars or Rebels, that doesn’t mean he couldn’t still appear in a future book, comic, or even The Mandalorian.
In fact, if there’s any place he should appear, it’s in the Star Wars live-action series. Hatred of the Mandalorians was Durge’s defining feature. But, in Legends canon, there weren’t many Mandalorians left for him to fight. If Durge were rebooted for The Mandalorian, it would bring with it a showdown 2,000 years in the making.