The Necrotic Bone is an item added by the Tinkers' Construct mod. Necrotic Bones are an uncommon drop from Wither Skeletons.
Uses
Necrotic Bones are used in the crafting of Heart Canisters. Necrotic Bones may also be used as an item modifier for Tinkers' Construct weapons to apply a life steal effect, which may be added to a weapon from a Tool Station.