Gunther was one of many human beings in the futuristic city of Haddyn whose body was mutated by the Sun's radiation. His mutation took the form of fish-like physiology which required him to live underwater in a giant tank. However, this didn't stop him from running a criminal operation that involved stealing artifacts of value or importance and selling them on for the right price. Gunther's best runner was a young thief named Melaka Fray, whose older sister Erin Fray was a member of the law and had a special interest in Gunther's activities.
Gunther's overall physiology resembles a merman, with human-like upper body, and a long serpentine tail instead of legs. His human-like body parts have some marine traits as well; his fingers for instance are webbed, and he has several growths on his arms and shoulders resembling seaweed. He also has gills on his neck; presumably, he has no lungs, as he can only breathe underwater. he has long, catfish-like barbels growing on his cheeks near the nose, which is human-like. His eyes are large, pure red and pupilless (and apparently lidless as well). He is completely hairless.
While his physical capabilities were never shown, he was able to defeat three lurks, suggesting he is stronger than normal humans and likely more durable as well. He also possesses great underwater maneuverability.