The Underworld

The Underworld (also known as hell) is the deepest biome in the game, reachable by digging past the stone layer. The Underworld can easily be differentiated from other biomes due to the background wall changing to a lava vein pattern. The Underworld contains partially destroyed buildings called Underworld Houses, which may contain Pots, Hellforges, and any kind of chest. The Underworld is the only biome where Hellstone, Ash Blocks, Hellforges, Fireblossoms, and Shadow Chests may be found. Healing potions found in Pots will only be Healing Potions rather than Lesser Healing Potions. Additionally, it contains stronger enemies.

The Underworld begins at around 3000-3200 feet on medium-sized worlds, but it may start at around 2000-2500 feet if you're lucky/unlucky.

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Monsters
 * Bone Serpent
 * Demon
 * Fire Imp
 * Hellbat
 * Lava Slime
 * Voodoo Demon
 * Wall of Flesh (Summonable boss)
 * Arch Demon (Console Exclusive)