The Magic Carcaj is an item added by the Better Dungeons mod that allows for infinite use of arrows with the Long bow. This does not work for the vanilla bow.
Crafting[]
Crafting Recipe
The magic Carcaj is crafted from 9 Arrow transformers which can be found throughout dungeons.
Exploits[]
As of Yogbox version 1.2.1, arrows that are shot from the player can be picked up. Because the magic carcaj is infinite, you can acquire an infinite amount of arrows by repeatedly shooting at the ground picking them up.