The foul stench combined with the possibility to move all across the north district unnoticed made the sewers the perfect vampire nest. Nosferatus of all levels were able to hunt to their belly's content turning the unsuspecting citizens into an easy meal. Granted, most of the citizens were regular humans, but their blood still sated their hunger and provided some manner of sustenance, especially for the lower level vampires.
By dawn, those who went out to hunt returned to their nest with their victims still unconscious to share the freshly acquired blood with their brethren. That way, even those who remained guarding the nest were able to feed. The same applied for the horror level nosferatu, who rarely got out to prevent getting spotted.
