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11 Planet 4546B
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33 Planet 4546B is the uncharted ocean world where the original Subnautica and Below Zero take place. It is a water-covered planet in the Ariadne Arm of the galaxy, designated only by its catalog number. The planet's surface is almost entirely ocean, with a few scattered islands. Subnautica 2 takes place on a different planet, Planet Zezura, but 4546B's events and lore provide context for the sequel.
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55 Geography
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77 The playable area of the original Subnautica sits within a volcanic crater approximately 2 kilometers in diameter. The crater is surrounded by the Crater Edge (also called the Dead Zone or Void), an open ocean expanse with no floor and no resources, patrolled by Ghost Leviathans that attack anyone who ventures beyond the map boundary.
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99 Depth ranges from the surface to approximately 1,700 meters in the Lava Lakes, the deepest accessible point. Two explorable islands exist: the Floating Island (buoyed above the water by Ancient Floaters) and Mountain Island (home to the Quarantine Enforcement Platform).
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1111 Biomes
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1313 Planet 4546B features over 20 distinct biomes, each with unique terrain, resources, creatures, and visual identity. The biomes are arranged in a roughly concentric pattern with shallower, safer biomes near the surface and progressively deeper, more dangerous environments below.
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1515 BiomeDepth RangeNotesSafe Shallows0-40mStarting area around Lifepod 5. Abundant basic resources.Kelp Forest30-160mTowering creepvine plants. Home to Stalkers.Grassy Plateaus80-170mFlat terrain with red grass. Common Seamoth fragments.Mushroom Forest120-250mGiant mushroom trees. Cyclops fragments found here.Blood Kelp Zone200-500mDark, foreboding biome with red bioluminescent kelp.Grand Reef120-480mDeep reef with Crabsquid and Ghost Leviathan juveniles.Dunes180-420mSandy expanse patrolled by 8 Reaper Leviathans.Lost River550-900mCave system with brine rivers. Disease Research Facility location.Inactive Lava Zone900-1,300mVolcanic caverns. Sea Dragon Leviathans.Lava Lakes1,300-1,700mDeepest biome. Primary Containment Facility and Sea Emperor.
1616 The Kharaa outbreak
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1818 Planet 4546B was the site of a catastrophic Kharaa Bacterium outbreak. The Architects brought the pathogen to the planet for study approximately 1,000 years before the events of the game. A containment breach at the Disease Research Facility in the Lost River released the bacterium into the planet's ecosystem, infecting wildlife and eventually the player. The Sea Emperor Leviathan's offspring produced Enzyme 42, which cured the entire ocean.
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2020 Architect presence
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2222 The Architects built four major facilities on 4546B: the Quarantine Enforcement Platform (Mountain Island), the Disease Research Facility (Lost River), the Alien Thermal Plant (Inactive Lava Zone), and the Primary Containment Facility (Lava Lakes). These structures contained alien technology, data terminals, and the imprisoned Sea Emperor. The QEP shot down any spacecraft attempting to leave or approach the planet, trapping Ryley Robinson until he cured the Kharaa and deactivated the weapon.
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2424 Human activity
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2626 Three human expeditions reached Planet 4546B:
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2828 ExpeditionWhenOutcomeDegasi~10 years before SubnauticaShip shot down by QEP. Three survivors built bases at increasing depths. Two died; Marguerit Maida survived.AuroraDuring SubnauticaAlterra Capital Ship shot down by QEP. Ryley Robinson was the sole surface survivor. He cured the Kharaa and escaped.Alterra research operationsDuring Below ZeroAlterra returned to Sector Zero for research. Robin Ayou investigated her sister's death.
2929 In Below Zero
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3131 Below Zero expands the explorable area of 4546B to include Sector Zero, an arctic region far from the original game's tropical crater. Two years after Ryley Robinson's escape, Alterra established research stations in the region. The environment includes ice sheets, glacial basins, underground cave networks, and deep-sea volcanic vents. Marguerit Maida from the Degasi crew has established a self-sufficient homestead in the area.
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3333 Connection to Subnautica 2
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3535 Subnautica 2 takes place on Planet Zezura, an entirely different alien ocean world. No characters, creatures, or vehicles from Planet 4546B appear in the sequel. The connection between the two planets is maintained through the broader universe: Alterra Corporation's ongoing activities, the Architects' ruins found on Zezura, and the Voices From Beyond audio drama that bridges the previous games and the sequel.