Magma Biome

The Magma Biome is the deepest, hottest underground biome in Oxygen Not Included, usually found at the core of a map. It is a source of extreme thermal energy rather than useful surface resources, and it is generally approached only when a colony needs access to heat, volcanoes, or the materials produced by cooling magma. The biome contains no Metal Ores, gases, plants, or critters.

Its exact composition depends on the variant. In the base version, the biome is filled with extremely hot magma at 1226.85–1526.85 °C. The Volcano Hole variant contains no liquid and instead includes solid magma; when that magma cools, it becomes Igneous Rock. This variant has 5 volcanoes. The Magma Vent variant appears higher than the base version and has a much lower temperature range, from 99.85–296.85 °C. The Volcano variant is the one used by the Volcanoes World Trait and can generate 8 volcanoes placed randomly on the map. In the Solid Magma variant, magma also cools into Igneous Rock.

Because the biome is so hot, its most important practical use is as a heat source. A well-designed setup can tap the core and feed that heat into Steam Turbines, turning the biome’s thermal energy into long-term power generation with very little maintenance. On a standard base-game map, a fully exploited magma core can sustain a colony for thousands of cycles. Spaced Out! maps generally offer less potential because they are smaller, and some may not have a magma core at all.

A few useful points to keep in mind:

• The biome is usually not worth exploring early unless a specific plan requires it.
• Its temperatures are high enough to damage unprepared Duplicants and melt or overheat nearby materials.
• Cooling magma produces Igneous Rock, which can be useful for construction and rock supply.
• Volcano variants make the biome especially valuable, since volcanoes can provide both heat and eruptive material for industrial setups.
• The safest way to interact with the biome is usually indirect extraction: isolate the heat, convert it to steam, and avoid exposing the colony itself to the core.

In game code, the Volcanic Biome is named Magma, and that naming reflects its role as the planet’s deepest heat reservoir.