The Corruption

See also: Underground Corruption. "Making the world evil..."

The Corruption is a hazardous surface biome that presents a dark purple "corrupted" theme. It may exist somewhere in a generated world, generally far from a player's original spawn point. It is the counterpart to The Crimson biome and its red gore theme. A generated world will contain only one of the two, chosen at random during world creation, each with a 50% chance of occurring. The two contain similar hazards, though each has its own unique enemies, items, and blocks. The tools, weapons, and armor obtained via Corruption materials are slightly less powerful than those obtained via Crimson materials, and Corruption enemies are also slightly less powerful.

The Corruption contains purple Grass and Trees, and hazards like Eater of Souls, Devourers, and Thorny Bushes. New players should generally avoid the Corruption until they obtain decent gear and a fair amount of health (via Heart Crystals). The Corruption also features a dark background with limited daylight and unique theme music.

The Corruption area that generates initially with the World is home to Chasms that lead to Shadow Orbs and Demon Altars. Corruption Chasms are especially hazardous to beginning players due to fall damage, and players who have not yet acquired fall protection (eg. Lucky Horseshoe) or a climbing aid (eg. Grappling Hooks), or a decent amount of Rope will have a tough or impossible time contending with them. Chasms are lined with Ebonstone, which can only be mined with a Nightmare Pickaxe/Deathbringer Pickaxe or higher.

Corruption, like Crimson, can also spread to areas not initially infected, though slowly. Corruption spreads much more quickly in Hardmode. Corruption can be seeded in new locations by the player using Corrupt Seeds. Chasms, Shadow Orbs, and Demon Altars will not spawn in Corruption that has formed through spreading; however, Corruption enemies like the Eater of Souls, as well as Thorny Bushes, will spawn. If enough Corruption takes hold in a new area, this area will adopt theme music, background, and water color.

Purification Powder can be used on corrupted blocks to turn them into their regular counterparts. "Purified" blocks can still become Corrupted again afterwards.

Contents
NOTE: View Underground Corruption for the mobs that spawn during Hardmode in and under the cavern layer.

Spread
In normal mode (pre-Hardmode worlds), corruption can spread, but only under limited conditions:
 * Corrupt grass can spread in a manner similar to normal grass, converting adjacent Dirt tiles with at least one side open to air (only in the Surface Layer).
 * Corrupt grass can also displace normal grass. Until version 1.2.4.1, this is true unless the grass has a Sunflower planted on it.
 * Corrupt grass may sprout Thorny Bushes, which can spread corrupt grass according to the same rules.

Naturally-occurring corruption will often be halted by various natural barriers (stone, desert, etc.) before it is even discovered, but care should be taken when creating an artificial corruption biome that it does not spread further than intended.

If all corruption and hallow blocks are purified, then when speaking to the Dryad about the world status, she will say "[name of world] is completely pure. You have done an amazing job!".

Hardmode
Once the Wall of Flesh is defeated, a world enters Hardmode. New areas of Corruption and Hallow are immediately created that extend from the Underworld up to the Surface, sometimes intersecting existing Corruption. Corruption begins spawning more dangerous enemies, such as the Corruptor, and underground, the Clinger.

Corruption spreads much more aggressively once the world is in hardmode:
 * In addition to corrupt grass, thorns and plants, Ebonstone, Ebonsand and Purple Ice also generate corruption.
 * Grass can still be converted to corrupt grass, and corrupt grass can cover new dirt as in regular mode.
 * Mud can now be converted into dirt.
 * Jungle grass can also be converted into corrupt grass (changing the underlying block type to dirt).
 * Jungle Thorny Bushes can be converted into Corruption Thorny Bushes.
 * Stone can be converted to Ebonstone.
 * Sand can be converted to Ebonsand.
 * Ice can be converted to Purple Ice.
 * Blocks that are up to three tiles away from an existing corrupt block can be converted (even if uncorruptible blocks are in the way).
 * Sunflowers can no longer stop the spread

The Corruption does not spread through other materials, even natural materials like clay and snow. Silt can be converted as part of the initial burst when you first defeat the Wall of Flesh, but not at other times.

In order to stop the spread of Corruption in Hardmode, the player must create a gap of at least three tiles containing empty space or non-corruptible blocks. Hallow blocks will also stop the spread of Corruption, but will spawn its own hazards as well.

Corrupted Desert
In Hardmode, Corruption spreads through Deserts, transforming it into Corrupted Desert. It is very similar to The Corruption: The theme music is the same, and enemies are the same, with the addition of Dark Mummies.

Sand is replaced by Ebonsand. Although their color is different, cacti still drop ordinary cactus when cut. Waterleaf is not able to grow in corrupted deserts.

Trivia

 * The game Anti-Idle features an area called the Corruption, based heavily on the Terraria biome.
 * The Corruption and its shadow orbs seems to be based heavily upon a story by H.P Lovecraft, "The Colour Out of Space". In the story a meteorite crashed near the small fictional town of Arkham, Massachusetts. The meteorite twisted the land, drove people insane, drained the life forces of anything around it, and deformed animals into grotesque abominations.
 * This may have something to do with why meteorites begin falling after a shadow orb is smashed.

History
Ebontrees now drop acorns.