Rust Biome

The Rust Biome is a hot underground biome characterized by Rust, Salt, and sulfur-rich terrain features, with variant-specific resources and temperatures. In its base form it spans a cool range of -16.15 to 6.85 °C, while the Warm variant reaches 24.85 to 39.85 °C, and the Frozen variant sits at -46.15 to -16.15 °C. Baseline generation contains no liquids, though Ethanol can appear through terrain features.

The biome’s composition changes by variant. The Warm variant contains Sulfur and is the most resource-rich of the three, featuring Big Obsidian Rock, Bleach Stone Deposit, Salt Deposit, and Sour Gas Room features. The Sour Gas Room contains Sour Gas and Salt Water, surrounded by Sulfur, Rust, and Mafic Rock. The Bleach Stone Deposit feature is a Chlorine and Bleach Stone room surrounded by Rust, Bleach Stone, and Mafic Rock. The Ethanol Lake feature is an Ethanol lake with Carbon Dioxide, surrounded by Mafic Rock and Rust. The Salt Deposit feature is a Salt deposit surrounded by Mafic Rock. The Frozen variant contains Snow and has no terrain feature.

The biome is useful for gas management and midgame industrial resource collection. All gases present here sink below oxygen, which makes airflow from oxygenated parts of the map easier to control. The resources found here can be fed into a Rust Deoxidizer to generate Chlorine Gas and Salt, making the biome a natural partner for chlorine production and salt recovery. If the goal is only to obtain the chlorine, melting Rust is a more efficient conversion than processing it through a Rust Deoxidizer.

A few practical points stand out:

• A continuously running Rust Deoxidizer requires exactly 5 Dasha Saltvines to absorb all of its Chlorine output.
• If the Saltvines are domesticated, this recovers about 36% of the spent salt; wild Saltvines recover about 6%.
• Dasha Saltvines are exclusive to this biome, so if the cluster does not include one, the GMO A-OK Achievement cannot be obtained unless a seed is provided by the Printing Pod.
• The biome’s high temperatures are usually not a major issue unless the map is already cold.
• Because the gases tend to sink, it is easier to isolate and route them than in many other biomes.

Overall, the Rust Biome is both a source of specialized materials and a convenient location for chlorine-focused industrial setups, especially when paired with Saltvines and Rust Deoxidizers.