The Newtralizer is a resident of Dimension X and like Boba Fett he's also a bounty hunter hired by Jabba the Hutt. As revealed in Pooh's Adventures of Teenage Mutant Ninja Turtles (Nickelodeon), he is Boba Fett's old partner before his disappearance during a mission to destroy the Kraang by Jabba the Hutt.
The Newtralizer is a heavily armored, alien Fire Belly Newt. He is primarily black, with an orange underbelly. The coloration of his underbelly forms a skull pattern. The Newtralizer is very muscular and bulky, easily dwarfing the Turtles in combat. He appears to be very intelligent, capable of using Kraang equipment and weaponry without issues.
His armor set includes a belt, a pair of shoulder plates (the right plate is far larger than the left), two straps that connect the belt and shoulder plates, a pair of armored bracelets, a pair of leg holsters with pouches and ammo types attached to them, and a pair of axe blades attached to his tail. He also wears a backpack with an antenna sticking out. It is likely a radio, but its exact purpose is unknown. He also carries three Kraang tentacles as trophies tied to his belt.