Marrow

The Marrow is a rare drop from Skeleton Archers deep underground. It turns any suitable arrow into a bone-like arrow that fires at an extremely high velocity in a straight path. Regardless of the type of Arrow used, they do not get their effects, if any, and once fired, the arrows cannot be retrieved.

If you plan to minimize costs, you should use Wooden Arrows since there are no effects to apply.

If you want to maximize damage output per shot, then using your highest damage arrow type is ideal. Cursed Arrows are damage-effective since they are relatively inexpensive, requiring only Wooden Arrows and Cursed Flames to make. Alternatively, the Venom Arrows can be used, however Vials of Venom are fairly costly, and Venom may be too good of a debuff to waste.

Trivia

 * Marrow is a substance found inside of bones.