The Underworld

"These obsidian and hellstone towers were once homes to thousands of...'people'."

The Underworld layer features 4 new enemies along with 3 new bosses. The Brimstone Crag biome generates in the left side of the Underworld, and an Underworld Bio-center Lab is located on the far-right side of the Underworld.

In Death Mode, without heat immunity gear, a player who is not standing in front of a wall will be inflicted with a new continuous debuff every six seconds, in the order: Weak, Slow, On Fire!, Confused, and then Burning after a total of 30 seconds. Additionally, lava geysers will occasionally erupt from Lava.