The zombie bone is an item on the Odd Old Man's wish list during Rag and Bone Man II. It is dropped by a variety of zombies. After the quest is completed you can no longer obtain this as a drop. The bone must be put into a pot of vinegar and boiled to create a polished zombie bone before giving it to the Odd Old Man.
Monster Combat level Quantity Rarity Zombie Varies 1 Common Undead lumberjack 40; 45; 50 1 Common Zombie swab 55 1 Common Zombie pirate 57 1 Common