Bone Serpent

The Bone Serpent is the strongest non-boss burrowing enemy, second only to the Eater of Worlds. Bone Serpents follow the Worm AI.Bone Serpents have a very rare chance of dropping a Flamelash or a Sunfury.

If you are looking to get the Flamelash or Sunfury try flooding the The Underworld with a lot of water. This will cause the Bone Serpent to move slowly through the water which makes it easy to kill.