Underground Desert

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BiomeBannerUndergroundDesert.png
A map view of an oval Underground Desert generated in 1.4.0.1 with a Pyramid and an Oasis.

The Underground Desert is a biome located directly underneath the main Desert of the world. The Desert above may generate different features which inform that the Underground Desert is underneath (see Surface Desert below for details). The Desert/Underground Desert pair will always generate on the same side of the world the Jungle is on.

The structure of the Underground Desert resembles that of a real-world ant hive, featuring numerous small caves mainly composed of Sandstone Blocks and Hardened Sand Blocks, which are connected in varying degrees. It is always either circular or oval in shape and is very large, rivaling even the Dungeon in size. Many types of Antlion enemies inhabit the Underground Desert, and it is also riddled with traps, namely Antlion Eggs, Rolling Cacti, and sand traps, making it a challenge to navigate.

The player is considered to be in an Underground Desert biome if they are in front of any Sandstone Walls or Hardened Sand Walls, and there are at least 1500 Sand Blocks, Hardened Sand Blocks, or Sandstone Blocks nearby.[1] (Also see the spawning mechanics section for details about Underground Desert enemy spawning.)

The Underground Desert becomes significantly more challenging in Hardmode. Along with harder enemies, it is extremely vulnerable to conversion by Corruption, Crimson, or Hallow due to Sand, Hardened Sand, and Sandstone all being susceptible to conversion. Conversion further strengthens the Underground Desert's enemies, and in Corruption and Crimson Underground Deserts causes the spawn of Desert Spirits.

Contents

Characters
During Hardmode:
Unique Drops
From all Ghouls:
From Basilisks:
From Lamias:
  • Moon MaskMoon Mask(Desktop, Console and Mobile versions)
  • Sun MaskSun Mask(Desktop, Console and Mobile versions)
  • Lamia setLamia set(Desktop, Console and Mobile versions)
  • Fried EggFried Egg(Desktop, Console and Mobile versions)
From any enemy in Hardmode:
  • Desert KeyDesert Key(Desktop, Console and Mobile versions)(1/2500 chance)
From the terrain:
Music

Surface Desert

A map view of an Underground Desert generated in 1.3.0.1 with a Pyramid. Note the large pit-type entrance.
For more details about the entrance, see Desert § Entrances to the Underground Desert.

The Desert above the Underground Desert may generate with various surface features, which can assist in locating and accessing the Underground Desert from the surface. Notably, it can contain an entrance which directly leads down into the Underground Desert.

It is also possible for one or more Oasis mini-biomes to be generated in the surface Desert, as well as one or more Pyramids. A Pyramid's tunnel will also often extend somewhat into the Underground Desert, providing another easy means of entry. However, the presence of an Oasis or Pyramid does not guarantee that the Underground Desert is below, as they can generate in any of the world's Deserts, regardless of which of them contains the Underground Desert biome.

Notes

A Corrupted Underground Desert
A partially Hallowed Underground Desert
  • Creating an artificial Underground Desert requires Treacherous Hardened Sand Walls or Treacherous Sandstone Walls, which are obtained through Shimmer transmutation and place the unsafe version of their respective wall. The regular Hardened Sand Walls and Sandstone Walls are considered safe when placed and will prevent enemy spawns.
    • Alternatively, the Clentaminator and Terraformer facilitate converting a variety of safe walls into unsafe Sandstone/Hardened Sand Walls. For instance, spraying Blue Solution onto safe Sandstone Walls will convert them into unsafe Pearlsandstone Walls. There are numerous other possibilities, like using Yellow Solution on safe Stone Walls or Green Solution on safe Hardened Ebonsand Walls. See Solutions § Conversions for the complete list.
  • The border between the Underground Desert and the Cavern layer often features pools of lava much closer to the surface than where lava would normally generate.

Spawning mechanics

None of the Underground Desert enemies require an actual Desert biome to spawn. Instead, they require certain unsafe walls. However, some enemies do have extra spawning conditions:

To successfully spawn an Underground Desert enemy on a selected tile, the following restrictions apply:

  • The selected tile can be any active (not actuated) solid block, which includes platforms or any other valid spawning surface.
  • The selected tile must be below 80 tiles above surface, and must be below the halfway point between surface and the top true world edge.[2]

Then, the following checks are performed to find applicable walls.[3] Applicable walls include any unsafe variant of Sandstone Wall or Hardened Sand Wall.[4]

  • If the selected tile is above cavern layer, below 200 tiles below the top true world edge, and the player is not in Dungeon biome, not in the zone of Celestial Pillars, and town NPCs near the player do not prevent enemy spawn:
    • 1/3 (33.33%) chance to perform this check: randomly selects a integer n between 5 and 14, then check tiles within a square area centered on the selected tile, with its side length being 2n+1 tiles (i.e. a square area between 11×11 and 29×29 tiles). If all tiles within this area are within the world, and one of the tile has an applicable wall, then Underground Desert enemies can be spawned.
    • If the above check is not performed, check the tile directly behind the player (the tile containing the top left corner of the player's hitbox). If it has an applicable wall, then Underground Desert enemies can be spawned.
  • If the conditions above are not met, then perform the following checks. Underground Desert enemies can be spawned if the following conditions are fulfilled:[5]
    • The selected tile must be more than 2 tiles from any true world edge.
    • The wall behind the selected tile or the tile above the selected tile must be applicable wall.

Tips

  • The Underground Desert enemies are very dangerous early on, so it is advised to have ample Grenades on hand as well as some form of movement-enhancing accessory to make it less difficult to deal with them. Gold/Platinum armor is recommended due to the high damage dealt by the Antlion Swarmers and Chargers.
  • Minions give several advantages in the Underground Desert that most other weapons do not. The Underground Desert's main dangers are fast-moving, knockback-resistant enemies and Rolling Cacti. Minions counteract these by being summonable on the other side of walls, reacting to quick-moving enemies without requiring player interactions, contributing knockback independently of the player's actions, and triggering Rolling Cacti remotely (which may require summoning them directly on the cacti multiple times or waiting to summon them until an enemy passes by).

Trivia

  • In the real world, larval antlions creates funnel-like pits in the ground and fling sand at prey that pass by. The funnel and burrow entrance types to the Underground Desert are presumably inspired by this.
  • Prior to 1.4.0.1, the Desert above the Underground Desert would always contain a large pit-style entrance. This made it easier to find and access the Underground Desert.

History

  • Desktop 1.4.4:
    • Increased the minimum size of Underground Deserts from 50% of the maximum size to 75% of the maximum. The maximum size has not increased.
    • Changed the Underground Desert enemy spawn conditions from a column of 50 unsafe walls to just the one behind the spawn block.
  • Desktop 1.4.0.1:
    • Added Sandstone Chests in world generation.
    • Generation changed to make the biome go to varying depths, making it much deeper than in previous versions.
    • Introduced a brand-new music track for the Underground Desert.
    • Lava now spawns at lower levels towards the edge of the biome.
    • The Desert above the Underground Desert may now generate other features than the funnel entrance, and the funnel design has also changed.

References

  1. Information taken from the Desktop version Desktop 1.4.4.9 source code, methods ExportTileCountsToMain() in Terraria.SceneMetrics.cs, UpdateBiomes() in Terraria.Player.cs, and SpawnNPC() in Terraria.NPC.cs, property EnoughTilesForDesert in Terraria.SceneMetrics.cs, and field DesertTileThreshold in Terraria.SceneMetrics.cs.
  2. Information taken from the Desktop version Desktop 1.4.4.9 source code, method checkUnderground() in Terraria.WorldGen.cs.
  3. Information taken from the Desktop version Desktop 1.4.4.9 source code, method SpawnNPC() in Terraria.NPC.cs.
  4. Information taken from the Desktop version Desktop 1.4.4.9 source code, field Sets.AllowsUndergroundDesertEnemiesToSpawn in Terraria.ID.WallID.cs.
  5. Information taken from the Desktop version Desktop 1.4.4.9 source code, method SpawnTileOrAboveHasAnyWallInSet() in Terraria.NPC.cs.