Chewed bones

Chewed bones are obtained from killing Mithril dragons in the Ancient Cavern. No other monsters in the Ancient Cavern will drop chewed bones, and looting the skeletons won't give chewed bones either (only mangled bones).

When these bones are put on a pyre ship and burnt, they will summon a Barbarian spirit, who will thank you for putting his soul to rest with an item. The reward may be a Dragon full helmet, various potions, runes or projectile ammo. Many players will attempt killing mithril dragons hoping for a dragon full helmet drop; if not successful will usually take the chewed bones to be burned in a pyre ship in hopes of getting a dragon full helmet again.

Burying chewed bones via a pyre ship will provide an exp bonus to burying any bones afterward. This exp bonus accumulates-- burying 2 chewed bones consecutively will provide an exp bonus for burying twice as many bones as burying one chewed bone.