Evil biome

An Evil Biome is a naturally spreading, hazardous biome that has generally negative effects on entities inside or around it. The Corruption or The Crimson will always spawn in a world. A generated world will only contain one of the two biomes, each with a 50/50 chance. A player can choose whether they want Corruption or Crimson to generate in their world or they can leave it up to the 50/50 setting. However, on the  Console version a player has a choice only if Hardmode has been entered in at least one world.

This biome is saved as the world's naturally generated Evil Biome, and determines:

• Whether Shadow Orbs or Crimson Hearts are generated
• Whether Demon Altars or Crimson Altars are generated
• Whether a Corruption Chest or Crimson Chest is generated in the Dungeon
• Whether Underground Corruption or Underground Crimson is created when the Wall of Flesh is defeated
• Whether Corruption- or Crimson-related blocks are seeded as Altars are smashed in Hardmode
• Whether some NPCs will sell Corruption- or Crimson-related items during a Blood Moon or Solar Eclipse
• Which Biome Mimic is spawned when a Key of Night is placed in a chest

It is possible to create an artificial Corruption/Crimson, seeding an area with the "wrong" evil. This is traditionally done with materials brought over from another world, but 1.4 provides a new option: If the Dryad is housed in a Graveyard during Hardmode, she will sell the other evil's Seeds during a Blood Moon.
Note: The type of Biome Key / Biome Key Mold  dropped by enemies is dependent on the biome the enemy is killed in, regardless of whether it is a "natural" biome or "artificial" biome. This will not however provide a Dungeon chest to go with the key.

The biome is predominately comprised of chasms made from infected stone (Ebonstone or Crimstone). However, the biome can overlap other biomes, providing corrupted versions of the Forest, Desert, Snow, Jungle or Ocean biomes. This can be evidenced by the presence of purple/red grass and Ebonwood/Shadewood trees, purple/red Cactus and Ebonsand/Crimsand, Purple Ice/Red Ice, or purple/red Palm Trees. Unfortunately, infected Jungle areas turn into corrupted Forest (with the mud converted to dirt). This makes such areas much harder to recover, though the presence of Chlorophyte ore can help.

While in Pre-Hardmode, the only biome capable of spreading the evil biomes is infected surface Forest, via infected grassy blocks (see below for details).

Corruption and Crimson counterparts

Certain items are exclusive to either The Corruption or to The Crimson.

The following items are considered counterparts to each other. It should be noted that counterparts do not necessarily share the same stats or behaviors.

The Corruption	The Crimson	Source
Musket	The Undertaker	Shadow Orbs / Crimson Hearts
Vilethorn	Crimson Rod
Ball O' Hurt	The Rotted Fork
Band of Starpower	Panic Necklace
Shadow Orb (item)	Crimson Heart (item)
Rotten Chunk	Vertebra	Corruption / Crimson enemies
Cursed Flame	Ichor
Vile Mushroom	Vicious Mushroom	Corrupt / Crimson grass
Demonite Ore	Crimtane Ore	also environment, Eye of Cthulhu
Shadow Scale	Tissue Sample	Eater of Worlds / Brain of Cthulhu
Eater of Worlds Mask	Brain of Cthulhu Mask
Eater of Worlds Trophy	Brain of Cthulhu Trophy
Eater's Bone	Bone Rattle
Worm Scarf	Brain of Confusion	(Treasure Bag)
Eater of Worlds Relic	Brain of Cthulhu Relic	Eater of Worlds / Brain of Cthulhu in Master Mode
Writhing Remains	Brain in a Jar
Dart Rifle	Dart Pistol	Corrupt Mimic / Crimson Mimic
Chain Guillotines	Fetid Baghnakhs
Clinger Staff	Life Drain
Putrid Scent	Flesh Knuckles
Worm Hook	Tendon Hook
Corrupt Seeds	Crimson Seeds	Eye of Cthulhu / Dryad
Vile Powder	Vicious Powder	Dryad, can be crafted
Purple Solution	Red Solution	Steampunker
Decay Chamber	Flesh Cloning Vat
Lesion Block	Flesh Block	Crafted
Scourge of the Corruptor	Vampire Knives	Corruption Chest / Crimson Chest

The Corruption

The Corruption presents a purple "corrupted" theme, with purple grass, trees and stone. Thorny Bushes and unique enemies (beginning with Eaters of Souls and Devourers) make the area dangerous and potentially deadly for newer players. The Eater of Worlds can only be summoned in the corruption. The Corruption contains deep vertical chasms (which can easily result in death from fall damage), with cross tunnels well below ground. Shadow Orbs appear deep underground, usually at or near the bottom of chasms. Destroying a world's first shadow orb will always drop a Musket and some Musket Balls, which automatically fulfills the criteria for the Arms Dealer to arrive. Destroying 3 shadow orbs will result in the spawning of the Eater of Worlds.

Corruption Contents

Characters

Pre-Hardmode:

• Eater of Souls
• Corrupt Goldfish
• Devourer
• Eater of Worlds(boss)

In Hardmode:

• Corruptor
• Corrupt Slime
• Shadow Slime 
• Slimer
• World Feeder

From killed Corrupt Slime/Shadow Slime:

• Slimeling(3 spawn at once)

Corrupted Desert:

• Dark Mummy
• Shadow Mummy 
• Bone Biter (Sandstorm only)

Underground Corruption:

• Cursed Hammer
• Shadow Hammer 
• Clinger
• Corrupt Mimic
• Vile GhoulWhile overlapping an Underground Desert
• Desert SpiritWhile overlapping an Underground Desert
• Corruption PigronWhile overlapping an Ice biome

Unique Treasures

From Shadow Orbs:

• Musket
• Musket Ball(Dropped with Musket)
• Ball O' Hurt
• Vilethorn
• Band of Starpower
• Shadow Orb (item)

Unique Drops

From Eater of Souls:

• Ancient Shadow armor
• Burger

From Eater of Souls, Devourer, Corruptor:

• Rotten Chunk

From Devourers:

• Worm Tooth

From Eater of Worlds:

• Demonite Ore
• Shadow Scale
• Eater's Bone
• Eater of Worlds Mask
• Eater of Worlds Trophy
• Treasure Bag(Drops the Worm Scarf in Expert Mode)
• Eater of Worlds Relic(Dropped in Master Mode)
• Writhing Remains(Dropped rarely in Master Mode)

From any enemy in Hardmode:

• Corruption Key(from any enemy, 1/2500 chance)
• Corruption Key Mold (from any enemy, 1/2500 chance)

Underground Corruption:

• Soul of Night(1/5 chance)

From World Feeders, Clingers and Vile Ghouls:

• Cursed Flame

From World Feeders:

• World Feeder Kite(on Windy Days)

From Corrupt Slimes and Slimelings:

• Blindfold

From Cursed Hammers:

• Nazar

From Shadow Hammers :

• Cobalt Bar
• Mythril Bar
• Adamantite Bar

From Corruptors:

• Vitamins

From Devourers and World Feeders:

• Suspicious Looking Apple

From World Feeders, Clingers, Corrupt Slimes, Slimelings, Cursed Hammers and Corruptors:

• Meat Grinder

From Dark Mummies:

• Blindfold
• Megaphone
• Mummy set

From Dark Mummies, Vile Ghouls and Bone Biters:

• Dark Shard

From Vile Ghouls:

• Ancient Cloth 

From Bone Biters:

• Shark Fin
• Nachos
• Sand Shark Kite(on Windy Days)

From Desert Spirits:

• Djinn's Curse 
• Desert Spirit Lamp 

From Pigrons:

• Bacon
• Pigron Minecart
• Pigron Kite(on Windy Days)

From Corrupt Mimics:

• Dart Rifle
• Chain Guillotines
• Clinger Staff
• Putrid Scent
• Worm Hook
• Greater Healing Potion
• Greater Mana Potion

From vegetation:

• Vile Mushroom
• Deathweed
• Deathweed Seeds(during Blood Moon)
• Ebonwood(from trees)
• Elderberry(from shaking trees)
• Blackcurrant(from shaking trees)

From terrain:

• Ebonstone Block

From terrain in overlapping Ice biome:

• Purple Ice Block

From terrain in overlapping Desert:

• Ebonsand Block
• Hardened Ebonsand Block
• Ebonsandstone Block

From Fishing:

• Ebonkoi
• Purple Clubberfish
• Corrupt Crate

From Fishing in Hardmode:

• Toxikarp
• Defiled Crate
• Scaly TruffleWhile overlapping an Ice biome

For Sale

From Painter:

• Lightless Chasms

Music

These music tracks play while the player is in the Corruption or Underground Corruption. Like most other tracks, they can be recorded with Music Boxes. On the  Desktop version, when Otherworldly music is enabled, tracks from Terraria: Otherworld will play instead.

Title	Music Box	Listen	Description
Corruption	Music Box (Corruption)		Its melody somewhat resembles the Overworld Day track but altered and slowed to sound much darker and more menacing.
Underground Corruption	Music Box (Underground Corruption)		This track is a combination of Corruption and Underground tracks, with a depressing and dark tone.
Corruption (Otherworldly)	Otherworldly Music Box (Corruption)		It's a dark, undulating track which features downtempo rock music.
Underground Corruption (Otherworldly)	Otherworldly Music Box (Underground Corruption)		Resembles its Otherworld surface counterpart, but is somewhat more aggressive.

The Crimson

Chasms of The Crimson

In contrast to the Corruption, the Crimson presents more of a red, gory theme, with red grass, stone, and foliage. Unique enemies that only appear on a crimson world include Blood Crawlers, Face Monsters and Crimeras. The Brain of Cthulhu, the alternative to the Eater of Worlds, can only be summoned in the crimson. Crimson-infected stone is called crimstone, and like its corruption counterpart, can only be mined with a Nightmare Pickaxe/Deathbringer Pickaxe or better. Like the corruption, the crimson contains deep chasms, but these are differently shaped: A winding tunnel from the surface leads to a large cavern, with secondary tunnels spreading downward from the cavern.These tunnels look quite like hands. While long falls are less of a hazard here, the area is still quite dangerous. Instead of Shadow Orbs, the Crimson contains Crimson Hearts, placed at or beyond the end of the secondary tunnels. Destroying a world's first crimson heart will drop The Undertaker with some Musket Balls, which, like their Corruption counterparts will fulfill the criteria for the Arms Dealer to arrive. Destroying 3 Crimson Hearts will result in the spawning of the Brain of Cthulhu.

Contents

Characters

Pre-Hardmode:

• Blood Crawler
• Vicious Goldfish
• Face Monster
• Crimera
• Brain of Cthulhu(boss)

In Hardmode:

• Herpling
• Crimslime
• Blood Jelly
• Blood Feeder

Crimson Desert:

• Blood Mummy
• Dark Mummy    
• Flesh Reaver (Sandstorm only)

Underground Crimson:

• Crimson Axe
• Ichor Sticker
• Floaty Gross
• Crimson Mimic
• Tainted GhoulWhile overlapping an Underground Desert
• Desert SpiritWhile overlapping an Underground Desert
• Crimson PigronWhile overlapping an Ice biome

Unique Treasures

From Crimson Hearts:

• The Undertaker
• The Rotted Fork
• Crimson Rod
• Panic Necklace
• Crimson Heart (item)

Unique Drops

From Crimera:

• Burger

From Blood Crawler, Crimera, Face Monster, Floaty Gross:

• Vertebrae

From Brain of Cthulhu:

• Crimtane Ore
• Tissue Sample
• Bone Rattle
• Brain of Cthulhu Trophy
• Brain of Cthulhu Mask
• Treasure Bag(Drops the Brain of Confusion in Expert Mode)
• Brain of Cthulhu Relic(Dropped in Master Mode)
• Brain in a Jar(Dropped rarely in Master Mode)

From any enemy in Hardmode:

• Crimson Key(from any enemy, 1/2500 chance)
• Crimson Key Mold (from any enemy, 1/2500 chance)

Underground Crimson:

• Soul of Night(1/5 chance)

From Ichor Stickers and Tainted Ghouls:

• Ichor

From Crimslimes :

• Blindfold

From Crimson Axes:

• Nazar

From Floaty Grosses:

• Vitamins

From Herplings, Crimslimes, Crimson Axes and Floaty Grosses:

• Meat Grinder

From Blood Mummies and Dark Mummies:

• Blindfold
• Megaphone
• Mummy set

From Blood/Dark Mummies, Tainted Ghouls, and Flesh Reavers:

• Dark Shard

From Tainted Ghouls:

• Ancient Cloth 

From Flesh Reavers:

• Shark Fin
• Nachos
• Sand Shark Kite(on Windy Days)

From Desert Spirits:

• Djinn's Curse 
• Desert Spirit Lamp 

From Pigrons:

• Bacon
• Pigron Minecart
• Pigron Kite(on Windy Days)

From Crimson Mimics:

• Dart Pistol
• Fetid Baghnakhs
• Life Drain
• Flesh Knuckles
• Tendon Hook
• Greater Healing Potion
• Greater Mana Potion

From vegetation:

• Vicious Mushroom
• Deathweed
• Deathweed Seeds(during Blood Moon)
• Shadewood(from trees)
• Blood Orange(from shaking trees)
• Rambutan(from shaking trees)

From terrain:

• Crimstone Block

From terrain in overlapping Ice biome:

• Red Ice Block

From terrain in overlapping Desert:

• Crimsand Block
• Hardened Crimsand Block
• Crimsandstone Block

From Fishing:

• Crimson Tigerfish
• Hemopiranha
• Crimson Crate

From Fishing in Hardmode:

• Bladetongue
• Hematic Crate
• Scaly TruffleWhile overlapping an Ice biome

For Sale

From Painter:

• Deadland Comes Alive

Music

These music tracks play while the player is in the Crimson or Underground Crimson. Like most other tracks, they can be recorded with Music Boxes. On the  Desktop version, when Otherworldly music is enabled, tracks from Terraria: Otherworld will play instead.

Title	Music Box	Listen	Description
Crimson	Music Box (Crimson)		An unnerving, dark, and unsettling theme with a faster pace than that of the Corruption. Its main melody comes near the end of the track.
Underground Crimson	Music Box (Underground Crimson)		A grim mix of the Underground and Crimson tracks.
Crimson (Otherworldly)	Otherworldly Music Box (Crimson)		A dark, ambient track which seems to feature some type of contrabass brass instrument for a 'gloomy' feeling and eventually becomes almost psychedelic-sounding.
Underground Crimson (Otherworldly)	Music Box (Otherworldly Underground Crimson)		A brooding and increasingly frantic track.

Spread

Main article: Biome spread

Both the Corruption and the Crimson will spread themselves, similar to the Hallow. This means that they slowly convert certain susceptible tiles that are in the vicinity of existing Corrupt/Crimson blocks. While their spreading capabilities are very limited during pre-Hardmode, they spread much faster and more aggressively after defeating the Wall of Flesh. Defeating Plantera for the first time reduces the overall spread speed of all three biomes by 1/2 (50%).

Corrupted and Crimson Deserts

Main articles: Corrupted Desert, Crimson Desert

A Corrupted Desert.

A Crimson Desert.

The evil biomes can overlap deserts, and in Hardmode, can spread through them, creating Corrupted and Crimson deserts. In the Corruption, sand is replaced with Ebonsand, and in the Crimson, sand is replaced with Crimsand. Unique enemies not found in the normal Corruption and Crimson can be found in the biome's desert variant.

Purification

See also: Guide:Maintaining world purity

A properly contained Corruption and Hallow, which, while not considered an evil biome, can eventually spread out of control.

In Hardmode, the Corruption or Crimson (like the Hallow) can spread out of control; without player efforts, the evil biome and Hallow will together take over the entire world.

In Pre-Hardmode, players can use Purification Powder to purify small portions of the corruption/crimson, and Sunflowers to block spread of infected grass. However, it is not until Hardmode that the spreading biomes become a major issue.

In Hardmode, a good strategy is to dig 3 tile wide tunnels around the corruption/crimson, containing it. However, near the surface Thorny Bushes can spread the corruption up to 6 blocks, so the tunnels there need to be 6 tiles wide or lined with non-corruptible blocks.

Removing the Corruption or Crimson wholesale, or reversing its spread in Hardmode, effectively requires the Clentaminator. This can be purchased for 2000000*2 (one of the most expensive items in the game) from the Steampunker, who arrives after at least one mechanical boss has been defeated. Using the Clentaminator with Green Solution (also purchased from the Steampunker) can purify large sections of the evil biomes. However, most players will want to keep some well-contained pockets of the biome, as the enemies there have unique drops (some of which are recommended to advance in the game).

The evil biomes are also blocked by the presence of the Hallow, and vice versa; even before obtaining the Clentaminator, seeding the Hallow is an alternate strategy to limit the spread of Corruption or Crimson. However, this may mean eventually having to deal with an out of control Hallow in the future.

Tips

• In 1.3, one-half of the world generation progress bar will be green, and the other half purple or red, depending on if the world is to have Corruption or Crimson. The step in world generation in which the Crimson is created is called "Making the world bloody", and the step in world generation in which the Corruption is created is called "Making the world evil". Also, a tree at the side of the world name in world selection has one green/normal side, the other purple/red (indicating Corruption/Crimson respectively). In Hardmode, part of the tree will be yellow, representing the Hallow.

Trivia

• In the  Desktop version, the world generated by the seed 05162020 contains both world evils.