This power allows the vampire to transform into a cloud of bats. While in Bat Form you become immune to mental attacks that specifically target your heart or mind, and gain 95% immunity to all other forms of mental damage. You also gain 50% immunity to crush damage, 53% to cut damage and 55% to stab damage.
While in Bat Form you will have a different inventory set, and be unable to use equipment. Your combat tables will all change to cloud tables, and your feet will provide you with a long-ranged travel technique. Your movement rate will also be increased to 66 outdoors and 6 indoors (i.e., the fastest possible).
As your Bat Form improves, so does the size and power of your cloud. Each rank gives you +1 Size and +5000 feet travel range, and the first 20 ranks also give you +1% immunity to all forms of damage except mental (so that at rank 20 you will have 75% immunity to stab damage, 95% immunity to mental, 73% immunity to cut, 70% immunity to crush and 20% immunity to all other forms of damage).
At rank 20, you unlock the 'merge' and 'split' commands. These require you to also have rank 20 in Summon Vermin.