The snake spine is an item on the Odd Old Man's wish list during Rag and Bone Man II. It is dropped by snakes and poisonous snakes. 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 snake spine before giving it to the Odd Old Man.
The level 35 snakes found on Mos Le'Harmless will not drop a snake spine.
