Thrumaladon is themed after Western Dragons much like its counterpart, Agillovern, however Thrumaladon incorporates many construction and machine elements into its design. The Pokémon has a much rougher appearance having larger midnight blue scales covering much of its body, some of which are large enough they protrude outwards. The Pokémon's jaw is much more angular appearing more rectangular in appearance, it has the slight appearance of a digger as its lower jaw is larger than its upper jaw. In addition the Pokémon's fangs in its lower jaw protrude out of its mouth making the appearance clearer. The Pokémon has a distinct brow that has darker scales than the rest of its body giving the Pokémon a constant gruff appearance. Thurmaladon has four large horns which all point directly straight perpendicular to the part of the head they protrude from, the horns have a basic cone shape to them with no spiralling. It has fish-like fins instead of ears although does have holes near the base of each fin that appear to be ear holes. the fins have skin between them that is light blue in colour. This light blue colour is also the same colour of its underbelly and neck which have a v-shape pattern of stripes on them.
The Pokémon has four large, muscular limbs each with seven claws on them, the Pokémon strangely has a thumb-like claw on each side of each foot and the other five claws behave like standard claws. Unlike Agillovern, Thurmaladon's limbs are all the same shape appearing similar to Agillovern's fore limbs in that their ankle joint is close to the toes. The scales around the top of each limb are quite large and form plate-like protective covers over the top of the Pokémon's legs. It has a comparatively short tail to the rest of its body although the tail is quite muscular and rigid, it is covered in a line of spikes that protrude from each side of the tail, the largest spikes are located closest to the base of the tail although none are close enough to prick the Pokémon's hind legs. Thurmaladon has two large wings that have a classic draconic appearance although the claws at the end of which finger of the wings appears similar to a hook on a crane and is able to move independently of the rest of the finger. The wings are roughly twice the size of the rest of the Pokémon when fully extended giving it a very large wingspan. The Pokémon's tail has a spade-like tip that's comprised of two very flat spikes.