- Greatly increased movement speed (+66.6%)
- Tiny size (good evasion and stealthy)
- +5 Dex
- Lower attack delay (-40%)
- Only for Vampires: a 1-in-8 chance of vampiric melee attack
- Hunger rate is reduced to 1
- Can't quaff potions, or evoke wands
- Spellcasting is disabled
- Can't open doors
- -5 Str
- All equipment, other than amulets, is melded
- Unarmed Combat base damage is 1+UC/5 (+ 1 if Vampire), instead of 3+UC
- 0 AC
- Vampires recover less hit points and nutrition (-50%) when they bite monsters with blood
You can acquire this ability in the following ways:
- Vampires gain access to Bat Form at level 3 through their unique Bat Form ability. This transformation is disabled while full and does not time out.
- Drawing a low-power Flight or Metamorphosis 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.
- Being affected by a beam of polymorph.
- Weapons of chaos may polymorph the attacker or the defender.
- Transmutations miscasts.
- Clouds of chaos.
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.