Ghoul's are not really humans or monsters, they are survivors of prolonged exposure to radiation that has lead to decaying of their flesh. However, on contrast to zombies, ghouls do not have rotten flesh, they have just mutated in a certain manner. During the mutation, some have managed to retain their humanity but there are some who have fallen into mental deterioration themselves. So make a wise choice while deciding on ghouls! Also, ghouls have obtained an extended lifespan and are immune to nuclear fallout.