How to Obtain, Farm, and Use Souls of Night in Terraria

• Defeat the Wall of Flesh to enter Hardmode. Then locate the Underground Corruption or Underground Crimson biomes.
• Enemies in the Underground Corruption or Underground Crimson biomes have a 20% chance of dropping a Soul of Night when killed within these biomes.
• You need 102 Souls of Night to craft every item that requires a Soul of Night, though some items may need to be crafted more than once.

Finding Souls of Night

Enter Hardmode. To get into Hardmode, you will need to kill a voodoo demon in order to get a Guide voodoo doll. Then you will need to travel deep into the underworld and throw the voodoo doll into lava to summon the Wall of Flesh. Defeat the Wall of Flesh to enter Hardmode. Make sure you are well prepared before summoning the Wall of Flesh. Have good armor and weapons. Be careful not to kill a voodoo demon over a lava pit to avoid accidentally summoning the Wall of Flesh.

Locate the Underground Crimson or Underground Corruption biome. These are both underground biomes that appear after the Wall of Flesh is defeated below the Cavern layer. The Underground Crimson biome is covered with red rocks and dirt and the Underground Corruption biome is covered with purple rocks and dirt.

Kill enemies in the biomes. Enemies have a 20% chance of dropping a Soul of Night when killed in the Underground Corruption or Underground Crimson layer.

Collect a Soul of Night. Souls a Night resemble a small glowing purple vortex. When an enemy drops a Soul of Night, walk over it to collect it.

Farming Souls of Night

Place 200 Ebonstone blocks or Crimson Blocks in the Stone layer. The stone layer features a background made of stone rather than dirt. Enemies have a 20% chance of dropping a Soul of Night when killed in the vicinity of 200 Ebonstone or Crimson blocks while in the Stone layer. Be careful where you decide to place these blocks. They will spread. Placing 200 Ebonstone blocks or Crimson blocks in the dungeon will allow you to collect Souls of Night by killing dungeon enemies.

Kill enemies. Even if the enemies do not natively spawn in the Underground Corruption or Underground Crimson biomes, they still have a 20% chance of dropping a Soul of Night as long as they are in the vicinity of 200 Ebonstone blocks or Crimson blocks.

Summon an Eater of Worlds. You can summon the Eater of Worlds using Worm Food. It has lots of different body parts that each drop items. Defeating the Eater of Worlds in the vicinity of 200 Ebonstone or Crimson blocks will drop about 5 to 10 Souls of Night.

Crafting Uses

Craft a Soul of Flame in a bottle. This can be used as a lantern in dark areas. This item doesn't require any crafting station to craft. You just need a bottle and a Soul of Night.

Craft a Key of Night. A Key of Night can be used to summon a corrupt or crimson mimic when it is placed in an empty chest. A Key of Night can be crafted from 15 Souls of Flame using a Workbench.

Craft a Decay Chamber. A Decay Chamber is a crafting station used to create corruption-themed furniture. It can be crafted from 10 Souls Night and a Flesh Cloning Vat with a Workbench and Ecto Mist.

Craft a Flesh Cloning Vat. A Flesh Cloning Vat is a crafting station used to create flesh-themed (crimson) furniture. It can be crafted from 10 Souls Night and a Decay Chamber with a Workbench and Ecto Mist.

Craft a Cursed Flame spell tome. This is a magic weapon that rapidly fires green cursed flames. It can be crafted from 1 Spell Tome, 20 Cursed Flames, and 15 Souls of Night using a Bookcase.

Craft a Golden Shower spell tome. This is a magic weapon that fires three arching golden streams with every click. It can be crafted from 1 Spell Tome, 20 Ichor, and 15 Souls of Night using a bookcase.

Craft a Cool Whip. A Cool Whip is a weapon that releases a snowball that chases nearby enemies upon making contact with another enemy. It can be crafted from 8 Souls of Light, 8 Souls of Night, and a Frost Core using a Mythril or Orichalcum anvil.

Craft a Dao of Pow. A Dao of Pow is a flail weapon that has an 80% chance of inflicting Confusion upon contact. It can be crafted from a Dark Shard, a Light Shard, 7 Souls of Night, and 7 Souls of Light using a Mythril or Orichalcum anvil.

Craft Demon Wings. Like all other wings in Terraria, Demon Wings allow the player to temporarily fly. These particular wings have a demonic look. They can be crafted from 10 Feathers, 20 Souls of Flight, and 15 Souls of Night using a Mythril or Orichalcum anvil.

Craft a Night Sensor. Sensors are mechanical devices that emit a signal under specific circumstances. The Night Sensor emits a signal when it is nighttime. It can be crafted from an iron bar, wire, and 5 Souls of Night using a Mythril or Orichalcum anvil.

Craft a Magical Harp. This is a magic weapon that fires ricocheting musical notes as projectiles. It can be crafted from a harp, 20 Crystal Shards, 8 Souls of Night, and 15 Souls of Sight using a Mythril or Orichalcum anvil.

Craft an Onyx Blaster. An Onyx Blaster is a shotgun-like weapon that fires a spread of four bullets and a dark-energy projectile that explodes on impact. It can be crafted from a Shotgun, 2 Dark Shards, and 10 Souls of Night using a Mythril or Orichalcum anvil.

Craft a Spirit Flame. A Spirit Flame is a magic weapon that summons a small, purple flame that hovers around the player and chases enemies, causing an explosion on impact. it can be crafted from a Desert Spirit Lamp, 2 Forbidden Fragments, and 12 Souls of Night using a Mythril or Orichalcum anvil.

Craft a Mechanical Skull. A Mechanical Skull is a boss-summoning item used to summon Skeletron Prime. It can only be used at night. It can be crafted from 30 bones, 5 iron bars, 3 Souls of Light, and 3 Souls of Night using a Mythril or Orichalcum anvil.

Craft a Mechanical Worm. A Mechanical Worm is a boss-summoning item used to summon The Destroyer (the Hardmode version of Eater of Worlds). It can only be used at night. It can be crafted from 6 Rotten Chunks or 6 Vertebra, 5 Iron Bars, and 6 Souls of Night using a Mythril or Orichalcum anvil.