Cloak of the Bat

While wearing this cloak, you gain _advantage_ on Dexterity (Stealth) checks. In addition, while in an area of _dim light or darkness_ , you gain the following benefits: * A fly speed of 40 feet while gripping the edges of the cloak with both hands. * Once between _long rests_ you can use an action to cast _polymorph_ on yourself, transforming into a bat. Unlike normal, you retain your Intelligence, Wisdom, and Charisma scores.

Source: Level Up Advanced 5e · OGL-1.0a · 5.1