Marsh Biome

The Marsh Biome is a temperate, swamp-like biome built around polluted water, slime, and algae. It is one of the early areas that usually appears around the starting region, and it can also generate in several variants with different terrain and temperature profiles. Depending on the variant, the biome may be composed of blob-shaped rooms, tall thin rooms, or geode-like pockets, and it can contain sand, sandstone, igneous rock, or a mix of slime, polluted water, water, and algae.

The most common and important resources in the Marsh Biome are polluted water and slime. Polluted water is the first thing worth controlling, since it can off-gas when exposed to open air; covering a pool with a thin layer of water prevents this. Slime is less immediately troublesome while buried, but once mined it can release polluted oxygen and often carries Slimelung germs, so excavation should be managed carefully. A simple method is to dig from below and let the slime fall into a liquid pool, which reduces exposure while keeping the material contained. Oxygen Masks or Atmo Suits also help protect Duplicants from germ exposure while working in the biome.

The biome can appear in several variants:

• Base Version and Steamy: typically human-warm, with temperatures around 24.85 to 39.85 °C.
• Slush: cold, around -46.15 to -16.15 °C.
• Inactive and Landing Site: human-warm, around 24.85 to 39.85 °C.

Feature-wise, the biome can contain different combinations of vents and ruins. The Base Version and Slush variants may include a Cool Steam Vent, a Natural Gas Geyser, and three ruins. The Steamy variant may include a Cool Steam Vent and three ruins. Inactive and Landing Site variants may contain two ruins.

The Marsh Biome can also support useful wildlife and plants. Pacu found here are a strong source of food, and Thimble Reeds make this biome an important source of reed fiber. In some variants, the biome is otherwise empty of plants and critters, while the buried terrain can still hide room features and mineral pockets.

A few practical points stand out:

• Polluted water is the main material to secure first, because it is easier to manage before excavation spreads it around.
• Slime is the bigger germ risk, especially after mining.
• The Slush variant is cold enough that Slimelung cannot survive there, so it is usually sterilized by the time Duplicants reach it.
• Because much of the biome is made of slime and polluted water, it is best approached with a plan for containment and sanitation.

In the game code, Marsh Biome is named HotMarsh.