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When in hardmode every enemy has a 0.025% (1 in 4000) chance of dropping a Dungeon Key. The type of Dungeon Key that is dropped depends on the biome you are currently in (Jungle, Corruption, Crimson, Hallow or Ice). It can be used to open a Dungeon Chest of the same color. Farming these keys can take multiple play sessions as they are very rare.
Biomes can be mixed - any of the designs below can be upgraded via biome-respective blocks to drop certain, or all, of the keys.
While it's Blood Moon or similar events, travel to the biome you want to find a key in. The massive amount of enemies will help you to get the key. File:Grinding box.PNG
An example
Meteor Heads spawned by a Meteorite biome (artificial or otherwise) can also drop the key for the biome it is contained in.
It is also possible to make a potential AFK farm by taking advantage of the Leaf Crystal granted by the Chlorophyte armor set. The crystal will automatically destroy any meteor heads in range with a single hit, resulting in very minimal effort on the user's end.
Another alternative, is to use the Pygmy Staff in conjunction with Tiki armor, confine yourself to a small location where the pygmies can't escape, and let them do all the work. Holding a water candle and using battle potions from time to time helps a ton with this method.
You can also use a box with the Spiky Ball traps from the temple and meteor heads
The most hassle-free way would be to have Turtle armor equipped and immerse your bottom half in honey or water.
It is a very easy way to simply use the Spiky Ball Trap method and keep your computer running while you go and do something else. Check back in a few hours and you might have at least one key. Sometimes a key will drop quickly, other times it will take several hours or days; it just depends on luck
Farming
It is preferred to build the farm underground, at least so far that the surface is not visible on the screen.
All farming methods can be made more effective by drinking Battle Potions and holding a water candle.
All methods and techniques listed here are in no way documented to be the best. If you come up with a better method, please post it here as a guide.
Killing Machine
This method can be hard to setup but is very effective and can be done while using any gear.
Dig out a medium sized room a little ways underground and place your materials like shown in the picture. The meteorite and wire can be placed however you like, just make sure the wire passes over every trap and the timer.
The finished product might look something like this:
Dig out a small room underground and place down your meteorite in any fashion you like. Now place your rope so you easily can hang in the middle of the room.
Now spawn all your pygmies and grab the rope. Like this:
Any obsidian item to be immune to the meteor blocks or a bunch of blocks not to be in touch with the meteor blocks
Cobalt Shield or upgrades thereof to be immune to knockback
The Build
Dig out a small pond in the (artificial or natural) meteor biome to pour honey or water. 2 blocks deep and 2 blocks wide, pour at least 2 buckets in the pond in order to be considered immersed and instantly extinguish the On Fire! debuff. You know you're enough immersed when the Water Candle doesn't fit in your hand while you select it (don't worry, even if it doesn't show, it still grants the monster spawn bonus).
The best: since the meteors crash in you, you immediately loot every drop and nothing is loss.
Enemies in a hallow/ice biome(pink ice) will drop hallow-keys.
Even while taking use of farms these keys are an extremely rare drop and may take anywhere up to 7+ hours to farm. If you run a dual-screen it is advised to run Terraria continuously in a window on your secondary monitor and glance over every now and then to check for key-drops.
Servers constantly run, so this is an alternative for afk'ing.
For single screen users, double click the windows task bar (that large thing on bottom of monitors) of the terraria window to minimize the game. It'll still run regardless of pause setting (? ), but sound will still play and mouse clicks still function. (old trick for statue farms)
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