Emily, Max, Pierce, Ronin, Zaren and Chuck encounter grouls while attempting to escape the catacombs. After a long chase during which Zaren and Chuck were taken and supposedly killed by the grouls, the rest managed to escape down a drainpipe. After Max steals the Mother Stone, Emily and her family escape the catacombs but encounter a large pack of grouls which Emily promptly destroys with her Amulet.
The grouls are humanoid creatures that walk on all fours. They seem to be completely hairless with sharp teeth and pale skin. Their ears are small and pointed and they lack visible noses. They have a row of spines running down their back and along their skeletal tail. Their eyes lack pupils and they have immensely sharp claws.
The grouls seem to be very social and live in large packs. They are very aggressive towards humans and possibly any other animal and will immediately attack and kill its prey without hesitation, which may be why they were used by the Guardian Council to protect their treasures. According to Max, they cannot swim.