The ulsio is a horrible Martian creature, somewhat analogous to the rat of Earth. It resembles a baby mouse, grown to the size of an Airdale terrier. The eyes are small and close together, nearly hidden within fleshy sockets. Its jaws are pure bone, extending beyond the flesh of its face to give the appearance of a rotting face, with five sharp and spade-like teeth in each jaw. It has a six legs with broad, blunt-taloned feet, which it uses to push dirt behind it when digging. The ulsio can be found almost anywhere underground, though there are apparently no ulsios to be found in the land of Bantoom, as they were considered a delicacy by the kaldanes, who hunted the creatures into regional extinction.