The Bat Form ability turns the player into a small and agile bat-like creature. This provides flight and greatly increases your movement speed and evasion, but it also disables most of your equipment, most items, most kinds of spellcasting, and drastically reduces your AC and Unarmed Combat damage. You can acquire this ability in the following ways:
- Vampires gain access to Bat Form at level 3. This improves at level 10, allowing you to enter Bat Form even when wearing cursed gear.
- Drawing a low-power Flight card may activate Bat Form.
- Jiyva may induce Bat Form (along with a vicious dose of magic contamination) at random as a penalty for abandoning him.
The most obvious use for Bat Form is for getting away from dangerous situations. Flight allows you to cross deep water or lava, and the speed and evasion boosts make it easy to get away from melee opponents. Enemies with ranged attacks will still be a threat, particularly if they have unavoidable or smite attacks.
Alternatively, it can be used to kite opponents if you happen to have the right abilities. Followers of Makhleb can still shoot blasts of destructive energy while in Bat Form, and the Breathe Flames and Spit Poison combat mutations still function. The Fangs mutation also adds to your Unarmed Combat damage, but bats usually don't want to be in melee.