Marrow

The Marrow is a rare drop from Skeleton Archers deep underground. It turns any suitable arrow into a Bone Arrow, which fires at an extremely high velocity in a straight path, regardless of the type of arrow used. This makes the Marrow a very cost effective weapon since it can use cheap or easily obtained arrows as effectively as higher tiered arrows, and ideal for eliminating common enemies from a distance without trouble.

However, any special effects that the arrows used are lost in the transformation. For this reason, the player should still keep a regular bow/repeater around, just in case you need to make use of special ammunition. For example, if you are fighting a boss, and the Marrow is the most powerful bow you have, you should still carry around a Cobalt Repeater (or another bow) in order to use Venom Arrows, Ichor Arrows, etc. before switching back to the Marrow.

Trivia

 * Marrow is a substance found inside of bones.