Underground Corruption

The Underground Corruption is the same as the Corruption, but it begins at the underground depth. It has even more dangerous enemies.

It is only accessible in the lowest of the Corruption chasms before the Wall of Flesh is killed, and until the Wall of Flesh is dispatched, it will be unable to spread. The Underground Corruption can only be made to stop spreading by surrounding it with Hallow or Underground Hallow biomes, which is notably difficult, as every trace of Corruption can spread more underground.