From his very good NIGHT WATCH:
“You couldn’t trust either of them. But they hated Keel with that gnawing, nerve-sapping hatred that only the mediocre can really bring to bear, and that was useful.”
Novelists are, first and foremost, observers of human behavior. This is why one can clearly see Gammas described and portrayed, though obviously not identified as such, throughout the literature of cultures that range from Heian Japan to modern America.