Underworld

The  is the hardest Pre-Hard Mode biome underground which requires high tier armor and weapons.

Getting to the Underworld
The Underworld is at the bottom of the world which may require a lot of digging or finding a cave which leads far down. The player will know if they are close because there will be lava in the way.

Mobs and bosses
The current mobs in the Underworld are:
 * Lava Bat/Hell Bat
 * Lava Slime
 * Fire Imp
 * Demon
 * Voodo Demon
 * Red Devil
 * Bone Serpent
 * Arch Demon (miniboss)
 * Wall of Flesh (boss)

Items you can get
From Shadow Chests From Terrain
 * Dark Lance
 * Sunfury
 * Flamelash
 * Flower Of Fire
 * Drax (very rare, bug)
 * Ash Block
 * Hellstone ore
 * Shadow Chest
 * Hellforge
 * Fireblossom