Underground Corruption

The Underground Corruption is a Hardmode Biome, being one of the biomes that spawns when the Wall of Flesh is defeated. It is the underground version of the surface-level Corruption, and appears at and below the cavern layer. It operates similarly to surface Hardmode Corruption, being comprised of Ebonstone and Ebonsand, though it spawns different enemies. Underground Corruption spreads just like surface Corruption, and similarly can not spread to The Hallow (nor to Underground Hallow).

Underground Corruption does not suppress the spawn of other underground and cavern enemies.

All enemies killed in the Underground Corruption have a chance to drop a Soul of Night.

''Note: Most characteristics of surface Corruption apply to the Underground Corruption, with the exception of the enemies that spawn. See The Corruption for more extensive information.''

Trivia

 * Even in pre-Hardmode, sometimes the Corruption can go so deep that the bottom would count as a Underground Corruption.