Bone Serpent

The Bone Serpent is an enemy found in The Underworld that can move through walls. It is the strongest of the non-boss enemies before defeating the Wall of Flesh. The only burrowing enemy stronger than the Bone Serpent are the Eater of Worlds, World Feeder and The Destoyer which are bosses.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.

The Bone Serpent is, like all burrowing enemies, immune to lava. Each section of a Bone Serpent will drop loot, but as they are usually defeated by destroying one segment of their bodies they seem to drop only one item. Applying large damage to multiple body sections at once with Dynamite will result in loot from every body section. This can drastically increase the loot gained from Bone Serpents.