Underground Hallow

The Underground Hallow is a version of the Hallow that appears at the cavern layer. Similar to Underground Corruption, Underground Hallow will spread through blocks that other Hallowed blocks come into contact with. Hallow is the only thing that Corruption will not spread through, and the opposite seems to be true. The Underground Hallow is the only biome in the game that has an abundance of Crystal Shards, which naturally spawn and re-grow in the biome.

In the Underground Hallow, there are some enemies that cannot be found anywhere else, all of which are very powerful.

The Underground Hallow, as with the Underground Corruption, do not generate on new worlds, but rather when the world enters hardmode after the Wall of Flesh has been killed. However, "importing" hallow blocks (such as pearlstone) to a non-hardmode world will allow the spawning of Chaos Elementals and possibly other Hallow-related enemies at the appropriate depth.

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

All enemies killed in the Underground Hallow have a chance to drop a Soul of Light.