The Bone Serpent is one of the burrowing monsters, capable of moving through blocks, and it can be found in The Underworld. It is the strongest of the non-boss enemies before defeating the Wall of Flesh. It is also equal in health with the Digger. In order to kill a Bone Serpent, you need to destroy at least one section. The tail can be "killed" without killing the rest of the Bone Serpent.