Ghoulrillas are very similar in appearance to old world gorillas. However, they appear to have undergone minor ghoulification. Resulting In scabs and scratches located around the body, with scraps of fur torn out as well. Their faces have become rough and worn, with many skinless patches,similar to ghoulified humans, and the eyes are dark often lacking pupils. The size of ghoulrillas varies fro. That of a Dog to gigantic brutes that dwarf a Super-Mutant. 

Ghoulrillas are likely to be the descendants of gorillas kept in zoos and safari parks before the bombs fell, but it is possible they may have been kept for biological experiments. Ghoulrillas are rare in the Wasteland often living away from civilisation deep in the irradiated forests. They live in groups of 2-12 adults often lead by a ghoulrilla king or Alpha. While mostly peaceful creatures, ghoulrillas will target anyone who enters their territory with extreme aggression and can become incredibly dangerous.