Catacombs (Lunar Veil)

Down The Well You Go

The Catacombs are a category of structures found in the Veil, Underground, Underground Desert, and Ocean.

The Catacombs have to be unlocked with a Catacombs Key dropped by the Wall of Flesh.

The main purpose of the Catacombs is them housing various Mini Bosses, summoned with Cursed Shards at their shrines that drop high amounts of resources and Weapons and Accessories. These Mini Bosses can be categorized in 3 Categories.

Trap, which houses The Cogwork and Sparn.
Water, which houses The Water Cogwork and Water Jellyfish.
Lava, which houses the Blazing Serpent and Pandora's Flamebox.

The Veil Biome's Catacombs are the main ones you should go to due to them containing Shrines for every Mini Boss and their obvious location compared to the other Catacombs.

However the-non Veil Catacombs each specialize in one type of Miniboss Category, as well as containing a Chest with a large supply of Cursed Shards.