Layers

There are currently 4 different layers of the underground, Identified by the background. The layers are:

Dirt Layer
===This is where the regular day and night cycle music plays, conventional mushrooms grow and the background wall resembles a regular craftable dirt wall. Zombies, demon eyes, bunnies, goldfish and all slimes excluding black and Mother slimes can spawn in this level.===

Rocky Dirt Layer
===This is the point where music changes to underground music, which can be used as a tool alongside the background itself to signal the true underground, where Glowing mushroom can be farmed, MOST crystal hearts, the majority of caves, and pools of water can be found, and the Skeleton, The Undead Miner, Mother slimes, black slimes, Pirrahnas, Cave bats and Giant Worms can all be found in this layer. The background wall here simply "exists farther back" and cannot be hammered away, but, because of the previous statement, you do not need to hammer the wall away to make your own background walls.===

Stone Layer
===In this layer, the background resemble the same as above, with the exception of the dirt look now being stone, and, like the previous layer, the wall "exists farther back" Same as last layer, but you will find ALOT more stone in this layer, and close to the bottom of it, you can find lava===

Underworld
===This is a total conversion, with a background of stone with veins of lava coursing through it, loads of lava, Hellstone and new enemies: The Fire Imp and the Bone Serpent. Here, the music will change to an eerie tune. Also in the underworld are small, randomly generated houses, made of hellstone brick. The hellstone brick will still burn you, so have an Obsidian Skull equipped. Layer not recommended for early players.===