Kaisopod

Kaisopod are medium-sized invertebrates that are found primarily in central and northern Terr'Aina. The are usually about 20-30 cm in length and greatly resemble oceanic Giant Isopods, but are typically darker in color and have more prominent eyes that glow slightly. Kaisopods are unique, however, in their strange defense mechanism. Inside of a Kaisopod, a small organ formed mostly of a hard natural material much like their exoskeletons exists. Within, a constant fire burns, providing the Kaisopod with warmth and their signature soft glow, a warning to predators. If punctured in any way, the Kaisopod will violently spew out a torrent of flames in that direction, often roasting attackers to a crisp with only minor damage to the Kaisopod itself.
However, Kaisopods are broadly considered to be pests. This is in part due to their diet, which fuels this life-fire - soft barks, light textiles, and most crucially, paper. Kaisopods are incredibly hardy, voracious creatures that are also hard to remove or dispose of safely, making them a constant nuisance in the regions where they live especially within libraries or homes. In particular, at the great libraries of Hon-shu of Xian, entire protocols have been enacted to deal with the fiery crustaceans, and any non-certified humanoid that disposes of a Kaisopod pays a hefty fine.
Kaisopod are actually an invasive species, a fact known by relatively few. They were originally from the Seashell Isles, where they had a small population that naturally consumed the bark of palm-like trees called paruma. However, at some point, they found their way onto mainland Terr'aina and quickly spread with human populations. Kaisopod may be pests, but do have several uses. They have been occasionally used as natural heating and are occasionally kept as pets, though this is not recommended. A Kaisopod's exoskeleton is also incredibly heat resilient and sometimes used in armor. Kaisopod "fuel" is also occasionally used as an ingredient in traditional medicine.