The Thrombax is a peculiar herbivore native to the continent of Uluria. This beast is… difficult to fully categorize. On the one hand, it is a mammal, as proven by the presence of fur and mammary glands. Furthermore, females of this species possess a pouch in which they keep their young until they are strong enough to follow their mother. However, the Thrombax can also lay eggs; females lay 1 to 2 eggs, which they then incubate in a nest for around a month. The resulting hatchling is small and fully reliant on its mother and needs to crawl into the mother's pouch to finish growing. This enables the female to forage for food and be on the lookout for predators without worrying about the safety of her vulnerable offspring.

With the traits mentioned above, it would be logical to categorize the Thrombax as a monotreme. This is where the problem with the classification arises. Monotremes are mammals that, similar to birds and reptiles, have a cloaca (a rear orifice that serves as the only opening for the digestive (rectum), reproductive, and urinary tracts ). Meanwhile, the Thrombax has an arrangement more like that of placental mammals. This alone disqualifies it from being part of the monotreme order.
While not confirmed, the current most prominent theory proposes that the Thrombax might be related to the Fauxauria of Elysium (such as the Durocranius and Imperia Cranus). The theory is based on their similar mammal-reptile features; however, the long distance between Uluria and Elysium (and no proof that the two land masses were ever connected), along with the marsupial traits of the Thrombax, puts a noticeable hole in that theory.

Most scholars are more willing to classify the Thrombax as a member of a separate order of mammals. For now, research is still ongoing.