Bat

A minion of the night sky. Some say it has secret power.
Overview
Bat is a creature found in the ore cave biome. When defeated, it turns into an item and can be used as a material for building a 
Since the 1.0.0400 Sorcerer Update, Bats can also produce Bone. This makes them more useful than a simple early cave creature, since they now provide a secondary resource in addition to their normal drop.
- Bats appear in cave areas tied to ore generation, so they are encountered while exploring deeper underground.
- Killing a Bat converts it into an item, which can be collected for later use.
- They are a required material source for constructing a Batiary.
- After version 1.0.0400, they can be processed into Bone, adding another reason to gather them.
Official description
A minion of the night sky. Some say it has secret power.