Biome Chests

Biome Chests are chests found in the Dungeon representative of the various biomes in Terraria, containing powerful weapons. Like other chests in Terraria, they are placed during world creation. There is only one of each type of Biome Chest in each world.

They are locked and can only be opened with a Biome Key from the appropriate biome, which can only be found by defeating enemies within the respective biomes once Hardmode is activated. Unless a key is obtained from another player or through inventory editing, the chests will be impossible to open before Hardmode. Instead, a character will need to return to the Dungeon once Hardmode is activated after obtaining the correct Biome Key for a chest (and face Hardmode Dungeon enemies) before being able to open a chest.

Biome Key Mold drops are incredibly rare (1/2500 chance of a key mold dropping from a defeated enemy in a biome). You'll probably need to defeat many thousands: 1732 to have a 50% chance, 3000 for 70%, and 5750 for 90%. With the right equipment and some time, you can set up a mold farm or grinder in the biome to get there sooner. To find what chance there is for at least one to drop for a given number of mobs, use the equation 1-(1-([drop chance]))^([number of mobs]). To find how many mobs are needed to obtain a certain percent chance it has dropped at least once, use ln(1-[%chance in decimal (70% = .7 etc...)])/ln(1-[drop chance]).

For navigation consider putting A LOT of torches or something recognizable in map view, so when you do eventually find the means to unlock them you don't have to waste time to search where the chest were exactly, rather recognize your marked positions via map markers. Rediscovering the special chest positions when you're swarmed in dungeon creeps isn't the best time investment.

Loot
Besides the rare items listed here, the chests also contain common items depending on the height they were found:


 * Surface
 * Underground
 * Caverns

Because Corruption and The Crimson are naturally exclusive to each world, a single world cannot contain both a Corruption Chest and a Crimson Chest.