Evil biomes



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 your world. A generated world will only contain one of the two biomes, with a 50/50 chance of one of them generating. If a player has entered hardmode in at least one world, they can choose whether they want the corruption or crimson to generate in their world. However, they can still leave it up to the 50/50 setting.

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 destroyed
 * Which corruption is seeded as Altars are smashed in Hardmode
 * Which Biome Mimic is spawned when a Key of Night is placed in a chest

These will not be affected by artificial Corruption/Crimson (which can be created from materials brought over from another world). The type of Biome Key /  dropped by enemies is dependent on the biome the enemy is killed in, regardless of whether it is a "natural" biome or "artificial" biome.

The biome is predominately comprised of chasms made from corrupted 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, a corrupted Jungle is merely turned into a corrupted Forest, and is only evidenced by a large quantity of water and mud blocks.

While in pre-Hardmode, the only biome capable of spreading corruption is corrupted surface Forest with its corrupted grassy blocks (see below for details).

Corruption and Crimson exclusives
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 share the same stats.

The Corruption
The Corruption presents a purple "corrupted" theme, with purple grass, trees and stone. Thorny Bushes and enemies like the Eater of Souls and Devourers exist in the biome, presenting dangerous and potentially deadly situations for newer players. The Eater of Worlds can only be summoned in the corruption. The Corruption contains deep chasms, which if not pursued carefully, can result in death from fall damage. Shadow Orbs exist in underground portions of the corruption, mostly at or near the bottom of chasms, in which case you will have to mine to them. Destroying your 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, so it is advised that you gear up before doing so.

The Crimson
The Crimson presents more of a red, gory theme, which differs it from its counterpart, the corruption. 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. Like the corruption, the crimson contains red grass, trees and stone. In the crimson, the stone is called crimstone, and can only be mined with a Nightmare Pickaxe/Deathbringer Pickaxe or better. Like the corruption, the crimson contains deep chasms, which can also result in death if not pursued carefully. Instead of shadow orbs, the crimson contains Crimson Hearts. Destroying your first crimson heart will give you the Undertaker and some musket balls, which, like shadow orbs, will instantly fulfill the criteria for the Arms Dealer to arrive. Destroying 3 crimson hearts will result in the spawning of the Brain of Cthulhu.

Spread
Both the Corruption and Crimson will spread throughout a world in pre-Hardmode, and more aggressively in Hardmode:


 * In pre-Hardmode, only and  can spread their respective evil biome; Stone, Sand , and Ice  will not convert other blocks and cannot be converted.
 * Corrupt Grass and Crimson Grass will spread similarly to, converting adjacent Dirt tiles with at least one side open to air (only in the Surface Layer).
 * Corrupt and Crimson grass can displace normal grass. This can be stopped in pre-Hardmode when the grass has a Sunflower planted on it.
 * Thorny Bushes can grow in the Corruption and Crimson a distance of 6 tiles in any direction, which can furthermore spread the Corruption and Crimson, even over non-corruptible blocks.
 * Non-corruptible blocks (blocks that Corruption and Crimson cannot spread to) include Wood (any sort), Clay, Ash, Silt, Obsidian, Ores, Gems and Bricks.
 * If the player brings Hallowed materials over from a Hardmode world, (created from Hallowed Seeds or Holy Water) will proceed to spread, converting both normal and Crimson grass, and competing with Corrupt grass. Other Hallowed blocks (,, and ) will have no effect.

Hardmode
In Hardmode, the Corruption and Crimson will spread much more aggressively, however defeating Plantera can slow the progression.


 * Sunflowers can no longer stop the spread.
 * Ebonsand,Crimsand, Ebonstone, Crimstone, Purple Ice and Red Ice will now spread their designated biomes.
 * Mud can now be converted to dirt, leaving the jungle vulnerable to the Corruption and Crimson.
 * Jungle Thorny Bushes can now be converted to Corruption and Crimson.
 * Blocks that are up to three tiles away from an existing Corrupt or Crimson block can be converted (even if incorruptible blocks are in the way).

Corrupted and Crimson Deserts
In Hardmode, the Corruption and Crimson can spread through the desert, therefore 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 also be found in the biome's desert variant.

Purification
In hardmode, the corruption and crimson can spread out of control, sometimes even taking over an entire world if nothing is done. Therefore, efforts must be made if you don't want your world to be overrun.

In pre-hardmode, one can use Purification Powder to remove portions of the corruption/crimson to help slow down the spread. However, it isn't until hardmode that the biomes present much of an issue.

In hardmode, a good strategy is to dig a 3 tile wide hole around the corruption/crimson, containing it. However, near the surface, Thorny Bushes can spread the corruption up to 6 blocks, so the hole needs to be 6 tiles wide.

However, if you want to make removing the corruption/crimson a feasible task in hardmode, obtaining the Clentaminator is recommended. Purchasing the Clentaminator requires. It can be purchased from the Steampunker, an NPC who arrives after at least one mechanical boss has been defeated. Purchase green solution from the steampunker, and use the clentaminator to wipe out the corruption/crimson. Note that you should keep small contained pockets of the biome, as the enemies that spawn within the corruption/crimson have unique drops that are required to advance in the game.

Tips

 * One way to know if your world has Corruption or Crimson is to ask the Guide. He will tell you to break a Crimson Heart if your world has Crimson, or to break a Shadow Orb if the world has Corruption.
 * 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.
 * In Expert mode, the Vampire Knives are highly useful in virtually all situations. However, the Crimson's boss accessory, the Brain of Confusion, pales heavily in comparison to its' Corrupt counterpart, the Worm Scarf, meaning that the two balance each other out.

邪恶生物群落