Vampire Bat Swarm

Although the typical vampire bat has a wingspan of 7 inches and doesn't pose a significant threat to larger prey alone (and indeed, these blood-drinkers can feed without their sleeping victims ever noticing), some unusually aggressive species of these bats hunt in deadly swarms. A churning cloud of vampire bats is much more dangerous than the sum of its individual parts and is capable of inflicting an overwhelming number of bleeding wounds in a frighteningly short span of time.

A wide range of bats dwell throughout the world. Most of these nocturnal animals are harmless insectivores, but deadly breeds of vampire bats and oversized bats the size of horses pose much more significant threats to adventurers.