- See also: Underground Crimson
The Crimson biome is an alternative to the Corruption. It has a 50% chance to be generated instead of Corruption during world generation. The red appearance of the biome, the flesh-resembling tree leaves and many gore-themed items obtained by Crimson materials suggests the biome's theme is based heavily on blood, instead of the darker, more shadow-like nature of the Corruption.
As with the Corruption, the Crimson has entrances to multiple Chasms; however, unlike the Corruption's vertical drops, the chasms in the Crimson cut at angles into the terrain and lead to a large, somewhat circular pocket underground that branches off into smaller veins. At the end of the veins are Crimson Hearts, the Crimson's equivalent of Shadow Orbs. Crimtane Ore and Crimson Altars replace the Corruption's Demonite Ore and Demon Altar respectively. The Crimson Altar functions the same as a Demon Altar, with only difference being the visual graphics. The Brain of Cthulhu is the Crimson version of the Eater of Worlds, being slightly more difficult. The tools, weapons and armor from the Crimson have minor stat boosts, in exchange for the Crimson's difficulty.
The Crimson can also be converted from any other biome using the Clentaminator with the Red Solution, only obtainable from the Steampunker during a blood moon in a Crimson world (she sells the Purple Solution in a Corruption world, obviously). During Hardmode, the spread of Crimson is the exact same as the Corruption; replacing Grass with Crimson Grass, and Sand with Crimsand. Stone Blocks are replaced with Crimstone and the Underground Crimson is formed, containing different monsters such as Ichor Sticker and Floaty Gross.
When the world generator generates the Crimson, any Sand that is within the biome is converted to Crimsand. Should the crimson overlap with the Snow Biome during world generation, it replaces Ice Blocks with Red Ice Blocks.
|Enemies||Unique treasures||Unique drops||For Sale|
From Demon Hearts:
From the terrain:
From the Painter:
- The step in world generation in which the Crimson is created is called "Making the world bloody." If you want a Crimson world, look for that step during creation.
- When you cut trees in the Crimson, they will not drop Acorns.
- Creating a new Crimson biome requires at least 200 corrupted blocks, such as Crimson grass, Crimstone, Crimsand or Red Ice Blocks. Although the Crimson replaces the Corruption at world generation, it does not prevent Corruption from being artificially created by importing corrupt materials to a world with Crimson and vice versa. Spreading remains normal.
- In Hardmode, all enemies in the Crimson have a chance of dropping a Crimson Key Mold.
- Unlike the Underground Corruption and Underground Hallow, the Underground Crimson has no unique music.
- The Clentaminator is an extremely useful tool for removing the Crimson. Green Solution is recommended, unless you want to replace it with another biome entirely.
- While normal mode Crimson enemies are based on blood (Blood Crawler, Face Monster), Crimson hardmode enemies seem to be based on pus (Floaty Gross, Ichor Sticker).
- What exactly the giant skeletal remains seen in the background are is unknown, though could possibly be the remains of Cthulhu. (View images  and )
- The Crimson may be a reference to War of the Worlds's (1898) Red weed, which was brought to earth by the martians. The trees in the background and the structures from the film have the same stringing flesh.
- The chasms that make up the Crimson, when viewed from the map, occasionally appear in the form of long twisting arms ending in hands, or neurons ending in dendrites.
- Due to the game containing various enemies related to Cthulhu, and the first boss released exclusively for this area being one of them, and the fact that you can use Crimstone to get Flesh Blocks, one could assume this biome is made of the body parts, remains, or even blood of Cthulhu.
- Also, Crimson, is a colour often described as the colour of blood, which again could confirm that the theory above could be true.