From publisher blurb: From the depths of the deepest underwater trench comes a horror unlike any ever seen. This monster might be the lost evolutionary link from when ancient humanity left the ocean to become land-dwelling creatures. Or this might be some sort of mutant human that decided land was not good enough and returned to the sea. The gill creature is a humanoid monster that has strong piscean traits: webbed digits, clawed fingers, gills, large eyes, and a wide, fish-like mouth filled with sharp teeth. The monsters to be found in these "YOUniversal Monster" products are new builds, designed to be fearsome threats in their own right. They have a variety of powers and abilities, ambitions, goals, and three different adventure ideas.