Board Thread:General Discussion/@comment-3967802-20131024044838/@comment-15781548-20131026181458

Well, The Crimson spreads like the hallow does. Through ice, sand, grass, and stone. (There might be more.) But The Crimson does not have unholy water. Also http://terraria.wikia.com/wiki/Topic:The_Corruption/The_Hallow/The_Crimson cannot spread through the jungle because the jungle has mud instead of dirt unless you are spreading the biome through the underground jungle walls. The only biome that can spread through the grass in the jungle biome is the Mushroom Biome.