Guide:Surviving in the Underworld

The Underworld is one of the most dangerous biomes in Terraria, and reasonably so; the best items and materials are found here, such as Hellstone. This guide will cover how to survive more easily the first time it's explored.

Recommended Gear

 * At least maximum Health (400) and Mana (200).
 * At minimum, use Shadow or Crimson armor. Class-specific armor can also be used:
 * Melee users should use Shadow armor.
 * Ranged users can use Necro armor or Fossil armor.
 * Magic users have a choice between Meteor and Jungle armors. The Wizard set with the Wizard Hat and Diamond Robe combines the best of the two, at the cost of defense.
 * Summoners have a choice between Bee armor and ( only) Obsidian armor.

Weapons

 * For a melee user, the Muramasa is the strongest sword available. The Blade of Grass can also be good due to its longer range. The Valor yoyo is also a very strong weapon.
 * For a ranged user, The Bee's Knees is the strongest bow available, but the Demon Bow/Tendon Bow are more easily obtained. The Minishark or the Boomstick are still the best guns that can be used.
 * For a mage, the Water Bolt is the best weapon available. The Aqua Scepter and the Magic Missile are decent secondary weapons.
 * Summoners should use the Hornet Staff, as the Slime Staff isn't very good against Underworld enemies, along with either the or  as secondary weapons.
 * Throwers should bring Bone Throwing Knives and Javelins, as they are the best weapons available for them.

Miscellaneous

 * Obsidian Skin Potions are needed to prevent damage by Lava, especially when mining Hellstone and dealing with Lava Slimes in Expert mode.
 * A Hook and/or Water Walking Potions are greatly recommended to move over lava lakes.
 * An Obsidian Skull can negate damage from hellstone.

First Visit
The Underworld can be visited at any time, however it isn't recommended to do so until the Dungeon has been fully explored and the player has the best gear available beforehand.

Hellstone, one of the main reasons to go to the Underworld, will burn players on contact if an Obsidian Skull is not equipped. It will also release lava when mined, so Obsidian Skin Potions or a Lava Charm should be used for easier mining. The equipment made from this material is very important against the Wall of Flesh and so on, so a lot of it should be mined.

There are big lava lakes everywhere, so mobility accessories like variants of the Cloud in a Bottle or Rocket Boots alongside a good Hook will make exploration easier.

The Hellstone Brick and Obsidian Brick towers are a relatively safe place to heal and regain mana. The bricks walls will block Demon's and Voodoo Demon's scythe attacks, and will prevent Hellbats or Lava Slimes from coming in. Make sure to take one of the Hellforges, as they are the only way to craft Hellstone Bars.

Subsequent Visit
On later trips to the Underworld, players should be much more prepared and ready to fight. The gear made from Hellstone is key for survival, as well as Obsidian Skin Potions.

Being more properly equipped, the enemies are much easier to kill. The most important thing to do is to find and kill Voodoo Demons, as the Guide Voodoo Doll is required to summon the Wall of Flesh and progress further in the game. It is recommended to obtain at least 5 dolls before progressing, as in Hardmode the boss is usually farmed for the Emblems and useful weapons that it drops.

Caution is required however, since the boss can be accidentally summoned if the Doll falls in a lava lake when they are killed.

Magic users should also kill the regular Demons for the Demon Scythe, while Melee players should look for a Cascade, as they are some of the best weapons to use against the Wall.

It is also good to open every Shadow Chest found, as they contain powerful weapons, potions and some useful ores. The Obsidian Pots should be smashed as well, as they contain better loot than those found anywhere else.

Pre-Hardmode
Hellbat
 * Hellbats are one of the most annoying monsters that appear in the Underworld. They aren't very strong, but they spawn very commonly and are quite small. A high damage weapon will usually deal with them without much trouble.

Lava Slime
 * Lava Slimes are not a big threat. They can be killed like any other slime. Their damage is low as well as their defense.
 * In Expert Mode, however, they can be a pain because they spawn lava when they die, so try not to get too close when you kill them. If you are trying to make a bridge for the Wall of Flesh, it is ideal to use solid blocks with holes so that the lava will not stay on the arena.

Fire Imp
 * Fire Imps fire 3 fireballs, then teleport to another location. If you can hit them once, they stop everything and don't move for about 2-3 seconds after each hit, making them defenseless. If you're not fast enough, however, they will teleport away and start firing again.
 * The fireballs can be destroyed with regular attacks, including a Pickaxe' s swing, so if the player mines carefully the Imp won't be too annoying when mining Hellstone.

Demons/Voodoo Demons
 * Demons shoot volleys of four Demon Scythes, which do a lot of damage on hit. The projectile, while easy to predict, can be hard to dodge, but it doesn't go through blocks, so fighting them inside the Obsidian Brick towers is much safer than a battle in the open.
 * As mentioned above, Voodoo Demons must be killed with caution, as they can summon the Wall of Flesh if the Voodoo Doll falls in lava.

Bone Serpents
 * Bone Serpents do a lot of damage if the head manages to hit the player, and they are very threatening when mining Hellstone and exploring due to their ability to dig through blocks. They can be easily killed with piercing weapons that hit multiple of its segments, such as a good Sword, a Water Bolt or ranged weapons with piercing ammo types like Jester arrows and Meteor shots.

Hardmode
In Hardmode, after a Mechanical Boss has been defeated, two more enemies will spawn:

Lava Bat
 * Lava Bats are the Hardmode version of Hellbats. They don't pose much of a threat, but don't let them get in groups, as they hit for 50 damage. You can use pre-hardmode weapons against these bats and kill them easily, but as you likely have more powerful weapons now, a Phasesaber or a ore sword are the best against them. They should be treated the same as Hellbats.

Red Devil
 * The true danger of the Underworld during Hardmode, Red Devils are Demon-like enemies, except much tougher. They are one of the deadliest enemies in the game, with 600 HP and being able to do 130 damage with their trident attack. The same strategies that work on Demons will work on Red Devils, however the player will need to be much more careful with their trident attack, as it will easily kill a player.