Swarm of Mortis Bats

Traits

Echolocation. The swarm can’t use its blindsight while deafened.

Keen Hearing. The swarm has advantage on Wisdom (Perception) checks that rely on hearing.

Swarm. The swarm can occupy another creature’s space and vice versa, and the swarm can move through any opening large enough for a Tiny bat. The swarm can’t regain hit points or gain temporary hit points.

Actions

Bite. The swarm attacks with its Bite.