The Direbats mod adds a new kind of bats. They are much larger than standard ones and can spawn both underground and on the surface, but only during the full moon. These bats are neutral, but become hostile if you disturb them, hang upside down, or receive sunlight. When attacking, they blind the player, and they can also steal objects with their large claws. This is the Forge version, and the Fabric mod you can download here.