Decayed Bat

Decayed Bat is a item. 5 of them can be given to the Tyashoi Alchemist in exchange for the Great Spook Chestplate. There is a 100% chance of the Decayed Bat being dropped from a killed bat.

Obtaining
It is obtained by killing any kind of Bats with a Wither Bow and Icy Arrows and will only drop if you have been given the quest from the Tyashoi Alchemist. One of the ways to consistently obtain this item is through the killing of bats in Dungeons. A lower Dungeon floor that is not too small is recommended when getting this item from Dungeons. Another way you can get this item is by spawning bats by using Roofed Forest Island on your private island.

Trivia
It's recommended to use the Runaan's Bow to aim and quickly swap to your Wither Bow.

Since Bats in the dungeons are killable with a simple bow shot using the Wither Bow, utilizing an Arrow Swapper to switch between Flint Arrows and Icy Arrows is an easy way to conserve your Icy Arrows when clearing the dungeon with the help of a Bow.

To obtain the Decayed Bat, a player must talk to Tyashoi Alchemist first.

It is recommended to put a box around the crystal so that the bats are trapped and made easier to be shot with an arrow if you use Roofed Forest Island to spawn the bat.