Guide:Artificial biomes
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Biomes in Terraria are based on where the player is and what blocks are nearby. Every biome is either naturally present in an area (e.g. Ocean) or can be artificially added to an area by the player. These artificial biomes are useful for enemy farming, fishing, and controlling NPC happiness, as well as drastically speeding up Biome Key farming by allowing for multiple drops at once. This guide will explain how to build and use artificial biomes.
Player biome
The game checks a 169x124 square for what biome the player is in, centered on the player's center[1]. For the player to be in a biome, there must be enough tiles that count towards that biome in the biome check range; this ranges from 125 tiles (for hallow) to 1500 tiles (for desert or snow).
The simplest way to have the player be counted as within a biome is to just place the appropriate tiles in a rectangle or cube. However, grass tiles like Jungle Grass can only be planted when an adjacent tile is open air; this means you need to include small air pockets for the grass to breathe. Make sure to use placement speed buffs to speed up the building process; Builder Potions and Ambrosia are great and relatively easy-to-get bonuses, while the Brick Layer is a massive bonus, but requires luck to get. Stacking all placement speed bonuses will half the time it takes to build an artificial biome.
NPCs determine what biome they are in when their dialogue box is opened, based on what biome the player is in.
Biome existence requirements
This content is transcluded from Biomes § Biome existence requirements.The area used for counting required tiles for the existence of biomes at a location is (Desktop, Console and Mobile versions) 84 / (Old-gen console and 3DS versions) 50 tiles to each side and (Desktop, Console and Mobile versions) 61 / (Old-gen console and 3DS versions) 42 below and (Desktop, Console and Mobile versions) 62 / (Old-gen console and 3DS versions) 44 above, measured from the player's center. This is the same range as for area buffs such as Campfires and Bast Statues. In the following table, the "Compatible biomes" column lists the biomes which can co-exist in the same general location, and has nothing to do with spreading mechanics.
| Name | Tile and location requirements[2][3] | Compatible biomes |
|---|---|---|
| Forest | Above the Underworld, no other biomes present. | Space, Surface, Underground, Cavern, Ocean |
| Graveyard(Desktop, Console and Mobile versions) | At least 5  Tombstones for basic biome, 7 Tombstones for all features. An additional Tombstone is required for each nearby Sunflower.
|
Not Underground, Cavern, Underworld, or Dungeon |
| Corruption | At least (Desktop, Console and Mobile versions) 300 / (Old-gen console and 3DS versions) 200 tiles of the following:
Each Sunflower increases the requirement by (Desktop, Console and Mobile versions) 80 / (Old-gen console and 3DS versions) 5, and each Hallow tile increases the requirement by 1. |
Not Hallow |
| Crimson | At least (Desktop, Console and Mobile versions) 300 / (Old-gen console and 3DS versions) 200 tiles of the following:
Each Sunflower increases the requirement by (Desktop, Console and Mobile versions) 80 / (Old-gen console and 3DS versions) 5, and each Hallow tile increases the requirement by 1.
|
Not Hallow |
| Mushroom | At least 100 of the following:
|
All |
| Jungle | At least (Desktop, Console and Mobile versions) 140 / (Old-gen console and 3DS versions) 80 of the following:
|
All |
| Hallow | At least (Desktop, Console and Mobile versions) 125 / (Old-gen console and 3DS versions) 100 of the following:
Each Corruption or Crimson tile increases the requirement by 1. |
Not Corruption or Crimson |
| Desert | At least (Desktop, Console and Mobile versions) 1,500 / (Old-gen console and 3DS versions) 1,000 of the following:
|
All |
| Ocean | At least 1,000 tiles of  Water.
The lateral location must be within 338 tiles (676 feet)[4][5] from either edge of the map. The vertical location must be above roughly the (Desktop, Console and Mobile versions) midpoint[5] / (3DS version) start[a] of the Underground layer. |
All |
| Snow | At least (Desktop, Console and Mobile versions) 1,500 / (Old-gen console and 3DS versions) 300 of the following: | All |
| Meteorite | At least (Desktop, Console and Mobile versions) 75 / (Old-gen console and 3DS versions) 50 tiles of  Meteorite
|
All |
| Dungeon | At least 250    Dungeon Bricks (regular or cracked(Desktop, Console and Mobile versions)) and any unsafe    Dungeon Brick Wall[b] below −4 feet.
|
All |
Building materials
While all worlds will generate with enough blocks for any number of artificial biomes, some blocks are easier to work with or gather than others. For instance, Sand Blocks and their variants are easy to place in large quantities compared to other desert blocks, Snow Blocks are incorruptible while Ice Blocks can be infected, and Jungle Grass Seeds can be gathered from the start of the game and spread on their own while Hive and Lihzahrd Bricks require much more effort to get.
Besides mining, there are other options for getting some biome blocks in large quantities:
- Grass Seeds, Corrupt Seeds, Crimson Seeds, Mushroom Grass Seeds and Hallowed Seeds can be bought in arbitrary quantities for making biomes.
- All of these are bought from the Dryad. The evil seeds for the evil your world does not have can be bought during Hardmode in a Graveyard, while Glowing Mushroom Seeds can be bought while she is in a Glowing Mushroom biome.
- Glowing Mushroom Seeds can be shimmered into Jungle Grass Seeds, making them effectively buyable as well.
- Ale can be bought from the Tavernkeep then shimmered to effectively buy Sand Blocks. The infected variants cannot be bought, however.
- The Clentaminator (sold by the Steampunker) can convert a massive amount of blocks very quickly for effective large-scale artificial biomes, but is rather expensive. If you can afford it, though, this is the best option for adding or removing large-scale infectious biomes, and especially for spawning the various Sand Shark variants.
- Thrown Powder and Thrown Water can generate moderate amounts of infected blocks on demand, but are rather slow for large-scale builds.
Some biomes require background walls, but the normal variants you can obtain are safe versions. Safe Sandstone Walls will still work for creating an Underground Desert (though this only gives its spawn rate without its unique enemy spawns), but otherwise you will have to shimmer background walls to get their unsafe variants. This works for Dungeon Brick Walls, Lihzahrd Brick Walls, Sandstone Walls, and Spider Walls, but not for Living Wood Walls or other wall types. The Clentaminator will also turn placed safe walls into their unsafe variants, allowing for unsafe artificial Dirt Wall or Grass Wall for Gnomes, for instance. To count as within a biome with a specific wall type, you need to stand in front of that wall type, i.e. an unsafe wall of the respective type must be behind the center of the player.
Some crafted enemy walls, like Spider Walls, require Ecto Mist, a passive effect seen in a Graveyard biome. Placing tombstones nearby is enough to get this biome and craft the walls, and you can remove the tombstones afterwards if needed.
Enemies
Most enemies are unaffected by what biome the player is in, instead only caring about what tiles they are spawning on and their height. Ichor Stickers can spawn in the Hallow, for instance, if provided Crimstone Blocks to spawn on. Some enemies do depend on biome, though, and in these cases you need to include the necessary blocks somewhere.
Generally the easiest place for this is on-screen, as enemies cannot spawn there. You can also prevent enemies from spawning on added Crimstone and similar by placing lava on top of the blocks, or putting them underneath other, incorruptible block types that spawn other enemies.
The biome check extends well above and below the vertical spawning range for enemies, allowing for artificial biomes to affect the farm from outside the border.
Depth and oceans
The layers of the world and position of the oceans affect biomes, but are in set positions. The ocean biome accounts for the outer 500 tiles of the world on each side, over the surface and extending to 40 tiles below the halfway point of the underground layer. The world's layers are space, surface, underground, cavern, and underworld, appearing in that order from top to bottom (in don't dig up, the underground and cavern layers are reversed). In general, you have to move to the ocean or a given layer, but you can create anything involving blocks.
Most desert biome blocks do not count for a desert in the ocean biome area, to prevent all the sand from creating a natural desert there. However, infected variants of Sand Blocks and Hardened Sand Blocks are not affected by this, making it still possible to build a desert in the ocean. The jungle biome is also explicitly disabled in the underworld[6]. Otherwise, however, almost any biome can be placed in any layer/area, even if they appear contradictory or to not have an effect; you can build a snow biome in the underworld and summon Deerclops there, for instance, and Lihzahrds can still spawn on the surface in an artificial Jungle Temple, though Golem will still enrage on the surface there. The exceptions are the Dungeon and Underground Desert, which both require the player to be below the surface to function.
The underground and cavern layer have a delay before applying most of their effects. Underground layer music only kicks in 34 tiles below the surface line, the Depth Meter only displays the player as in the cavern layer 47 tiles below the cavern line, and the spawn rates for each layer kick in at 68 tiles beneath their respective boundaries.
The Forest biome is effectively the absence of biome, only present when no other biome is and the player is on the surface. It is the only biome that cannot be used alongside other biomes for NPC happiness considerations, as it instead gets overwritten entirely.
Besides specifically the Underground Desert, which has unique background walls not seen on the surface, the only definitive difference between a surface biome and its underground variant is height. Building an artificial Crimson biome in the cavern layer makes that an Underground Crimson biome in function.
Truffle
The Truffle will only move into a house on the surface with a nearby Glowing Mushroom biome. Rather than using the player's biome check, the game checks the same range as the corrupted housing check - around 45 tiles past each house border. Making an artificial Glowing Mushroom biome with nearby housing can allow for the Truffle to naturally move in during Hardmode, as well as let the Dryad sell Glowing Mushroom Seeds for an easier time spreading Mushroom and Jungle Grass. You can also add a Glowing Mushroom biome to existing Jungle housing or vice versa, which will make the Dryad happier and give more freedom with what Pylon to use in that area.
Travel
Different layers and the oceans can be difficult to reach quickly due to the sheer distance. There are a number of approaches to making these trips faster:
- Hellevator
A Rail system
Running on Asphalt
A Teleporter Network
A Pylon Network(Desktop, Console and Mobile versions)- Teleporting items such as a
Magic Mirror, 
Magic Conch(Desktop, Console and Mobile versions), or a 
Demon Conch(Desktop, Console and Mobile versions).
References
- ↑ Information taken from the
Desktop 1.4.4.9 source code, method ScanAndExportToMain()inSceneMetric.cs. Due to how edge cases are handled, tiles 62 tiles above the player are checked for biomes, but tiles 62 tiles below the player are not. This is why the height of the biome check area is even instead of odd. - ↑ Information taken from the Desktop 1.4.4.9 source code, methods
UpdateBiomes()inTerraria.Player.csandExportTileCountsToMain()inTerraria.SceneMetrics.cs. - ↑ Information taken from the Desktop 1.3.5.3 source code, methods
UpdateBiomes()inTerraria.Player.csandPreRenderPhase()inTerraria.Lighting.cs. - ↑ Players cannot come within 41 tiles from the absolute edge of the map. Thus, from a player's perspective, the oceans end roughly 338 tiles (686 feet) from either lateral end, but technically they actually end 380 tiles (760 feet) from either end. Information taken from the Desktop 1.4.0.5 source code, method
BordersMovement()inTerraria.Player.cs. There may be inaccuracies, as the current Desktop version is 1.4.4.9.
- ↑ 5.0 5.1 Information taken from the Desktop 1.4.0.5 source code, method
oceanDepths()inTerraria.WorldGen.cs. There may be inaccuracies, as the current Desktop version is 1.4.4.9.
- ↑ Information taken from the Desktop 1.4.4.9 source code, method
UpdateBiomes()inPlayer.cs.
- ↑ On Desktop,
Console, and 
Mobile, the Ocean vertically ends at a point 40 tiles (80 feet) deeper than the middle of the Underground layer. On 
, the Ocean vertically ends at a point 10 tiles (20 feet) deeper than the start of the Underground layer – i.e. ending at a depth of approximately 23 feet, as shown by a Depth Meter.
- ↑ On
Old-gen console and versions, the requirement for unsafe (naturally placed) walls makes a artificial Dungeon biome nearly impossible and, if accomplished, it would be unable to spawn Hardmode Dungeon enemies or Cursed Skulls (as they require naturally-placed Dungeon Brick Walls). It appears that the only option for expanding the space in which Hardmode Dungeon enemies can spawn is by mining blocks already inside the area in which the Dungeon originally generated, without damaging any naturally-placed walls they are covering. On Desktop, Console, and Mobile versions, the Cursed Dungeon Brick Walls, obtained via Shimmer, allow placing unsafe walls.
