Cloak of Wicked Wings

From a distance, this long, black cloak appears to be in tatters, but a closer inspection reveals that it is sewn from numerous scraps of cloth and shaped like bat wings. While wearing this cloak, you can use your action to cast polymorph on yourself, transforming into a swarm of bats. While in the form of a swarm of bats, you retain your Intelligence, Wisdom, and Charisma scores. In addition, you don't need to maintain concentration on the spell, and the transformation lasts for 1 hour, until you use a bonus action to revert to your normal form, or until you drop to 0 hit points or die. If you are a druid with the Wild Shape feature, this transformation instead lasts as long as your Wild Shape lasts. The cloak can't be used this way again until the next dawn.