Rotspawn

The Rotspawn are a group of hostile mobs native to The Otherside, and have invaded The Undergarden. They are defined internally by the "undergarden:rotspawn" entity tag.

Behavior
The Rotling, Rotwalker, and Rotbeast all behave the same way. Rotspawn wander around randomly. When they spot a player, passive mob, or Stoneborn, they run towards it and attack. Rotspawn are damaged by Shard Torches and receive a damage multiplier from Utherium swords. They will also attack any entity that attacks it.

Spawning Rules
Rotspawn can spawn on any solid block with a light level below 7. They have an increased chance of spawning in the Barren Abyss.