Source: Pathfinder Bestiary, pg(s). 294
Shulns resemble hairless, molelike rodents around twenty feet in length. They possess four muscular legs, which end in serrated claws, and a short tail. They have large, protruding incisors, and four small, nearly imperceptible eyes. Their snouts sport several small whiskers, which allow them to sense movement in the air and the ground.
As they mature, shulns naturally deposit adamantine within their bones, teeth and claws. This process renders the affected organs nearly indestructible, and allows shulns to quickly burrow through stone and earth.
Shulns are predators and possess large appetites, and will eat nearly everything they can catch. However, their favored prey are large invertebrates, primarily cave worms. They track their prey using their sensory whiskers, and subdue it using a powerful paralytic toxin injected through their bites. This toxin is one of the few capable of affecting cave worms in this manner, allowing shulns to subdue the otherwise nearly unstoppable worms.
Shulns are often hunted in order to harvest the adamantine within their skeletal systems. They are also sought out as guardians in regions of the Darklands with large populations of cave worms. Shulns are difficult animals to keep, as they are obstinate and bad-tempered and their habit of digging into rock can compromise underground settlements' stability, but Darklands natives often see these as acceptable costs for possessing insurance against cave worm intrusions. Travelers seeking protection over a journey sometimes attempt to acquire a shuln's preserved saliva instead, in order to avoid the difficulties of leading a shuln over a long journey.
In the Great Beyond
Shuln-like creatures are known to inhabit the Plane of Earth. These specimens are more intelligent and much larger than their Material Plane counterparts, and are capable of casting earth-related primal magic. Like Material Plane shulns, however, they are eager predators of cave worms. Some scholars speculate that these shulns are ancestral to the Material Plane populations, and that the species had its origin in the Plane of Earth.