You can find this on Lamorak Cave (east area). It’s on the area of the Lamorak Cave where it leads you to Bors ruins (You need to have the earth ability to break the rock).
Recommended Level: 36-40
Recommended time frame: After defeating medusa, you will pass this cave so you can reach water trial shrine.
Armatize with Mikleo and use your Blistering Fang (2nd hidden arte; tilt up). Maintain your distance with the bat and you will this battle easily, simply run around him, wait until he use the ultrasonic attack, then counter attack.