Rat Swarm (encyclopedia)
A rat swarm typically consists of a biting, roiling mass of hundreds of disease-ridden rats driven to uncharacteristic heights of aggression by fantastic and overwhelming hunger. In such numbers, they become voracious hunters, capable of killing a full-grown human with hundreds of bites. Rat swarms are often found in the sewers of large human settlements.
Rat swarms surround and attack any warm-blooded prey in their path.