Hell on Earth: Gimme Shelter
"Trogs" are Mutants for whom the extreme and rapid cellular changes of their mutations resulted in a loss of sentience and reason. They often live in the irradiated ruins of pre-war cities, where the ambient radiation often causes new and worsening mutations, deforming the trogs even further as they age.
Trogs gather in large groups of a hundred or more, bowing to the strongest and most fearsome of the lot. Settling things peacefully means screaming at the top of their lungs, beating their chests, or smashing rubble with their clubs. When that doesn’t work, trogs fight to the death while the rest gather around and watch the carnage. They are exceptionally territorial and respond to intrusions with swift and noisy violence.