A giant monster of possibly mythical origins living in the swamps. It was composed of both animal and vegetable matter, and could fire mud at its opponent, trapping it. The beast was possibly under the influence of an old cajun, and its attacks prompted H.E.A.T. to look into it. Zilla Junior fought the creature, but became trapped by the mud. Later it fought him again and escaped into the swamp, but Zilla was restrained from following by Nick.
The Swamp Beast is fully at home in aquatic habitats, and has a camouflaged body which disguises the creature while in the swamp. The bayou terror can unleash streams of sticky mud from the pores in its back, and also appears to have the power to simply disappear into nothingness. It also has the physical strength to stand its ground against Zilla Junior.
- The Swamp Beast bears similarities to the comic book characters Swamp Thing and Man Thing, possibly paying tributes, since both of them are made of slimy vegetable substances and live in swamps. It could be also a mutated surinam toad.