Echolocation. The bat can't use its blindsight while deafened.
Keen Hearing. The bat has advantage on Wisdom (Perception) checks that rely on hearing.
Bite. Melee Weapon Attack: +0 to hit, reach 5 ft., one creature. Hit: 3 (1d4+1) piercing damage and 1 cold damage.
Sonic Screech (recharge 6). Ranged Attack: reach 15 ft., up to 3 creatures in range, DC 11 Constitution Saving Throw, on a fail, the creature gets 5 (1d8+1) physic damage, on a succesfull saving throw the creature isn't affected. A deafened creature or an Artic Swamp Bat is not affected by the screech.
Description
An evil wizard changed a swamp into a frozen swamp with the help of a white dragon, but when they did that some of the local flora and fauna changed too. This bat is also changed and is about 2 feet tall, has a snowwhite skin, piercing blue eyes and his fangs look like frozen shards of eyes. They live in groups with a leader, the queen, and make their lairs in caves, which they decorate with shiny things they find or steal.