I recently spawned and killed the Eye of Cthulu, I got 2 crimson seeds, I planted them and it now says (when I ask my dryad) "Central City (my world) is now 7% Crimson! You are so close." What does this mean? Have I destroyed my world? What is happening? I am terrified.
Terraria – Terarria what happens with Crimson Seeds
terraria
Best Answer
To answer your question, I need to explain a couple of things first, starting with biomes. Biomes are defined when there are enough of a certain biome's specific blocks close together; so for example, a lot of snow blocks makes a snow biome, and a lot of crimson grass or Crimstone makes a Crimson biome.
Crimson biomes spawn naturally during world generation, they have a cave-like entrance to a deep opening in hard, unmineable Crimstone, where you can find tough enemies and Crimson Hearts. From the start of the game, Crimson will spread over grass, turning it red and expanding the biome, but cannot spread to any other kind of block, except for the vines and thorns it creates. In most cases, a Crimson biome will quickly get contained by a patch of stone that it cannot cross or something similar.
The Crimson Seeds you got from slaying the Eye of Cthulhu are related, but also not. When you plant a Crimson Seed, you create a single patch of Crimson-infected grass, and nothing else. Now, if left unattended, that patch can spread to more grass, but it's unlikely to create a biome because it most likely won't reach the amount of blocks needed to create a biome, since it cannot spread to stone, but only grass.
The Dryad gives you a status report on how much of the world is infected by the Crimson, as she would like to see the world completely cleansed of it. The two Crimson Seeds you planted are incredibly small compared to the naturally occurring biomes, and the fact that you planted them is not related to the fact that the Dryad is telling you about how much Crimson is in the world.