Marsh Biome

Marsh Biome is a mid-game biome that commonly contains large deposits of Slime and pools of Polluted Water, along with plant and rock pockets typical of wet, lowland areas. It appears in several world variants (Base Version, Slush, Inactive, Steamy, and Landing Site) and often includes blob rooms filled with Carbon Dioxide, Polluted Water, Slime and Algae; some maps also include geodes containing Sand, Sandstone and Igneous Rock. The biome frequently hosts mechanical points of interest such as Cool Steam Vents and Natural Gas Geysers, and several ruin clusters provide exploration value and loot.

The biome’s composition varies by variant. Base, Steamy and Inactive variants present blob and tall thin rooms with Carbon Dioxide, Polluted Water, Slime and Algae. The Slush variant replaces most liquid pockets with colder water and Polluted Water and is centered around low temperatures (around -30 °C), which prevents Slimelung germ survival and usually sterilizes the biome. Geodes with Sand, Sandstone and Igneous Rock can appear in both blob and slush rooms. Points of interest include: Base and Slush commonly have 1 Cool Steam Vent, 1 Natural Gas Geyser and 3 ruins; Steamy has 1 Cool Steam Vent and 3 ruins; Inactive and Landing Site variants show 2 ruins.

Marsh Biome is a rich source of raw materials and food but also an environmental and biological hazard. The two most plentiful and potentially harmful resources are Polluted Water and Slime. Polluted Water presents immediate fluid management challenges and should be addressed first; covering a pool with a thin layer of clean water prevents off-gassing. Slime veins off-gas only when mined, which makes them easier to control, but slime is often infected with Slimelung germs. When mining Slime, mining from below so the slime drops into a liquid pool (Polluted Water is effective) prevents slime blocks from releasing into the base and reduces germ spread. Personal protective equipment such as Oxygen Masks or Atmo Suits prevents Duplicant exposure to germs during excavation.

Practical notes for settlement and exploitation:

• Treat Polluted Water as the priority hazard: isolate or seal pools, or cap them with a layer of clean water to stop off-gassing.
• Handle Slime by mining into a liquid catchment; keep a liquid column underneath veins so extracted slime falls into liquid rather than exposing air.
• In the Slush variant, low temperatures (~-30 °C) naturally kill Slimelung, making exploration safer.
• Expect Carbon Dioxide pockets; plan ventilation and gas management to avoid CO2 buildup in bases.
• Use the Pacu and Thimble Reeds where present as sources of Food and biomass resources.
• Exploit geodes for Sand, Sandstone and Igneous Rock; ruins contain useful loot and often justify careful excavation.
• Be mindful of nearby geysers and vents: a Natural Gas Geyser and Cool Steam Vent commonly occur in the biome and can be integrated into base power and cooling systems.

Technical note: in the game code the Marsh Biome is named HotMarsh.