One important way by which humans survived the Troll Occupation of the Big Rubble was through the Pavis priests. Strategic use of City Harmony, small fire, earth, and water elementals, and the Support spell, especially aided by the presence of Lord Pavis, was enough to let humans survive in their strongholds.
For three centuries, the humans of the Big Rubble survived in their little strongholds, relying on the Pavis cult, troll internecine conflict, and the dangers of the Big Rubble to prevent their extermination. No doubt the Kaggroka clan found it easier to make the humans pay a tribute in food and service than to trying to eliminate them. In the world within the great walls, they were the rulers, but their rule was constantly unsteady and often challenged.
Another key to human survival was the approximately 200 dwarfs in the Big Rubble. The Flintnail cult is closely associated with Pavis and the dwarfs aided their human allies.