As soon as you enter Hardmode in Terraria, the world's Corruption, Crimson, and the new Hallow biome all start to expand outwards. Rapidly. If left to their own devices, these biomes will eventually swallow your entire world, destroying your NPC villages and making life generally difficult.
Related: Terraria: Best Placement For All NPCs
Thankfully, there are a variety of different ways you can remove Corruption and Crimson from your Hardmode world. This guide covers everything you can do to prepare for Hardmode's evil biome spreading, and what you can do in the endgame to remove it entirely.
Updated June 14th, 2022 by Jacqueline Zalace: Corruption and Crimson can be quite a pain to deal with. Because of this, we've updated this guide with more information on how to remove both of these evil biomes.
Corruption and Crimson are the main evil biomes of your world. Each world will spawn with either a Corruption or Crimson biome, though there are one or two rare seeds that will spawn both. You can choose whether you start with a Corruption or Crimson world before you start generating it.
The biome will determine which bosses you face, like the Brain of Cthulhu for the Crimson and the Eater of Worlds for Corruption. This will also dictate what sort of armor and weapons you can create before you enter into Hardmode.
Overall, these two modes are the same difficulty, so it's up to you which one you want to face in your world.
Both biomes will slowly spread, even before Hardmode. They convert nearby blocks to the same biome at a very slow rate. Corruption and Crimson can spread through sand, mud, grass, stone, pretty much every default natural block in Hardmode, but in pre-Hardmode, they only spread through grass and bushes. Conv
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