BAT

A bat, flitting in the darkness outside, took the wrong turn as it made its nightly rounds and came in through the window which had been left healthfully open. It then proceeded to circle the room in the aimless fat-headed fashion habitual with bats, who are notoriously among the less intellectually gifted of God's creatures. Show me a bat, says the old proverb, and I will show you something that ought to be in some kind of a home.
A Pelican at Blandings, by P. G. Wodehouse

Name: bat
Difficulty: 2
Base level: 0
Base experience: 6
Speed: 22
Base AC: 8
Base MR: 0
Alignment: 0
Frequency: Very rare, normally appears in small groups
Genocidable: Yes
ATTACK:
Bite: 1d4
Weight: 20
Nutritional value: 20
Size: tiny
Resistances: None
Resistances conveyed by eating: None

A bat can fly/float. It has an animal body. It has no hands. It is a carnivore.

Name: giant bat
Difficulty: 3
Base level: 2
Base experience: 22
Speed: 22
Base AC: 7
Base MR: 0
Alignment: 0
Frequency: Quite rare
Genocidable: Yes
ATTACK:
Bite: 1d6
Weight: 30
Nutritional value: 30
Size: small
Resistances: None
Resistances conveyed by eating: None

A giant bat can fly/float. It has an animal body. It has no hands. It is a carnivore.

Name: vampire bat
Difficulty: 7
Base level: 5
Base experience: 66
Speed: 20
Base AC: 6
Base MR: 0
Alignment: 0
Frequency: Quite rare
Genocidable: Yes
ATTACKS:
Bite: 1d6
Bite: Strength draining poison
Weight: 30
Nutritional value: 20
Size: small
Resistances: sleep, poison
Resistances conveyed by eating: None

A vampire bat can fly/float. Due to its unusual body chemistry, It has no need to breathe. It has an animal body. It has no hands. A vampire bat can regenerate itself. It is poisonous if eaten.