A decryption computer is a late-game crafting station that lets you unlock encrypted items and access hidden content

The decryption computer in Terraria is a functional crafting station you build in the Crimson or Corruption biome. Once placed, it lets you decrypt items that are otherwise locked — mainly the Biome Keys and certain late-game loot. You need it to progress toward the Dungeon and to craft some of the most powerful gear available in the game.

Building one requires materials from the hardmode biomes and a bit of preparation, but the process is straightforward once you know what to gather and where to place it.

Key Takeaways

  • A decryption computer requires 20 Souls of Night, 10 Hallowed Bars, and 15 Ectoplasm, all found or crafted in hardmode.
  • You craft it at a Mythril or Orichalcum Anvil, the same stations you use for most hardmode equipment.
  • The computer must be placed in either a Crimson or Corruption biome to function and decrypt items.
  • Biome Keys are the main items you decrypt with it, and each key opens a different biome chest in the Dungeon.

Materials you need to craft a decryption computer

You need three materials in specific amounts: 20 Souls of Night, 10 Hallowed Bars, and 15 Ectoplasm. All three come from hardmode enemies and biomes, so you cannot build one until you have defeated the Wall of Flesh and entered hardmode.

Souls of Night drop from Eater of Souls and Corruptors in the Corruption biome, or from Crimeras and Herpling in the Crimson biome. You need 20 total, so plan on spending time in whichever evil biome you have. Hallowed Bars are crafted from Hallowed Ore, which spawns in the Hallow biome after you defeat the Wall of Flesh. Smelt the ore in a furnace, then craft bars at an anvil — you need 10 bars, which means 30 Hallowed Ore. Ectoplasm drops from Wraiths and Poltergeists in the Dungeon, so you need to have access to the Dungeon already. Collect 15 pieces.

Where to craft the decryption computer

Take your materials to a Mythril Anvil or Orichalcum Anvil — these are the hardmode anvils that drop from hardmode ore or are crafted from hardmode bars. The recipe appears in the anvil's menu once you have all three materials. Craft it there, and you will receive the decryption computer as a placeable item in your inventory.

You do not need to be in any particular biome to craft it. Craft it anywhere you have an anvil set up, then carry it to where you want to place it.

How to place and use the decryption computer

The decryption computer must be placed in either a Crimson or Corruption biome to work. Stand in the evil biome of your choice, open your inventory, select the decryption computer, and place it like any other furniture. It takes up a 3×3 space, so make sure you have room.

Once placed, walk up to it and press the interact button (default is the right mouse button on PC). A menu opens showing any encrypted items in your inventory. Select the item you want to decrypt, and it will unlock when ready. The computer does not consume the item or require any additional materials — it straightforward removes the encryption.

What items you can decrypt

The main items you decrypt are the Biome Keys: the Corruption Key, Crimson Key, Hallowed Key, and Jungle Key. Each one opens a corresponding biome chest in the Dungeon, which holds unique weapons and accessories. You find encrypted biome keys as drops from enemies in their respective biomes or as loot in chests.

Some players also use the decryption computer to unlock other encrypted loot that appears in late-game content. Always check your inventory for any items marked as encrypted — the decryption computer will show them in its menu.

Common mistakes to avoid

The most common mistake is placing the decryption computer in the wrong biome. It will not work in the Surface, Underground, or any biome other than Crimson or Corruption. If you place it and the menu does not open, move it to the evil biome.

Another mistake is gathering Ectoplasm before you can safely farm the Dungeon. Wraiths and Poltergeists are dangerous enemies, and you need decent gear to collect 15 Ectoplasm without dying repeatedly. Wait until you have hardmode armor and weapons before you try to farm the Dungeon for this material.

Frequently Asked Questions

Can I place a decryption computer anywhere in the Corruption or Crimson?

Yes. As long as the biome blocks are present where you place it, the computer will function. You can place it deep underground, on the surface, or anywhere in between, as long as it is in the Corruption or Crimson biome.

Do I need more than one decryption computer?

No. One computer decrypts all encrypted items. You only need to build one unless you want to place extras in different biomes for convenience.

What happens if I decrypt a Biome Key and then lose it?

Once decrypted, the key stays decrypted. If you lose it, you can find another encrypted copy and decrypt it again at the computer.

Can I decrypt items in hardmode before defeating any bosses?

You need to defeat the Wall of Flesh to enter hardmode and access the materials for the computer. Once you have the computer built, you can decrypt items when ready.

What if I do not have a Crimson biome, only Corruption?

The computer works in either biome. If your world only has Corruption, place it there. You do not need both biomes present.