Bone Serpent

thumb|300px|right The Bone Serpent is an enemy found in The Underworld that can move through walls. It is the strongest non-boss burrowing enemy, the only burrowing enemy stronger than the Bone Serpent is the Eater of Worlds.

Every segment of his body has 150 HP, except the tail, which has 200 HP but 3 higher defense, and the head, which has 120 HP and 1 lower defense. The Bone Serpent's HP is not shared between those parts. In order to kill him, you need to destroy at least one part of him.

The Bone Serpent, like all burrowing enemies, is immune to lava. The Bone Serpent may, rarely, drop a Sunfury, Flamelash, or Flower of Fire. 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 and is a great tactic when searching for the elusive Sunfury.

It has been found that instead of disappearing, the Bone Serpent will frequently die offscreen without any player interference. This has been the source of the rumor about them being affected by lava. There has been at least one instance in which the Eater of Worlds died offscreen, and had its loot found next to a torch - this may point to a bug in which torches can kill them. In addition, unlike other non-boss monsters, the Bone Serpent will die a few seconds after the player dies. This behavior is usually reserved for boss monsters; it is unknown if this is intentional.

The Bone Serpent may also live if the back end closer to the tail is destroyed, it may be a bug. (unconfirmed)