The expedition descent in Casualties: Unknown spans 11 primary procedural layers and 7 specialized sub-layers or structures, plunging from the cold rocky shafts of Layer 1 (Gravel Lands) through flooded fungal caverns, scorching geothermal vents, and radioactive ruins down to Layer 11 (Where We Must Reach).
Use the interactive filter and search bar below to compare depth meters, ambient temperatures, primary hazards, and Mercenary quest roles across all 11 main layers.
| Name | Layer # | Depth Span | Biome Profile | Avg Temp | Temperature Range | Primary Hazards | Native Enemies | Traps & Hazards | Flora & Harvestables | Structures & Chip Sites | Progression & Quest Role |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | 0–300m | Cavernous Cold Rock & Clay | 15.0°C | 12.6°C to 18.5°C | Fall damage, Spike traps, Geysers, Shade crawlers | Shade crawler | Geyser, Jump pad, Spike trap | Glowplant, Geotree, Hydreed, Stoneplant, Leadbush, Ceiling rye | Wooden structures, Malfunctioning Tech-Ball (Mercenary quest) | Break open the Tech-Ball to obtain and use the Nano-tech scanner before leaving Layer 1 | |
| 2 | 300–600m | Pitch-Black Flooded Caves | 17.5°C | 12.5°C to 21.4°C | Total darkness, Groundwater & Lumalgae flooding, Cave tick infestations | Shade crawler, Cave tick | Geyser, Jump pad, Spike trap, Barbed fence, Bear trap, Cave tick spawner | Glowplant, Geotree, Hydreed, Stoneplant, Leadbush, Ceiling rye | Wooden structures, Concrete structures, REL-Hyper-Regeneration Booster chip site | Contains the REL-Hyper-Regeneration Booster chip site (Chip 1 of 6) | |
| 3 | 600–900m | Arid Sandstone & Viscous Oil Chasms | 26.6°C | 12.4°C to 35.6°C | Viscous Oil pools (exhaustion drowning), Automated Turrets, Landmines, Tall vertical drops | Shade crawler, Sand stalker | Jump pad, Barbed fence, Bear trap, Turret, Stalactite, Landmine, Waste pipe | Sand rose, Sandvine, Cactus, Dried bush, Brownshroom, Glowplant, Stoneplant | Wooden structures, Recharging station vault (often oil-flooded), Micro-SINGLEBTR 1CHRG capacitor site | Contains the Micro-SINGLEBTR 1CHRG capacitor chip site (Chip 2 of 6) | |
| 4 | 900–1200m | Radioactive Industrial Ruins | 25.8°C | -20.4°C to 38.6°C | Radiation sickness, Radwater pools, Radioactive barrels, Ceiling turrets, Extreme thermal swings | Shade crawler, Cave tick, Sand stalker | Turret, Ceiling turret, Landmine, Barbed fence, Bear trap, Radioactive barrel, Spent fuel, Sound cannon | Glowplant, Stoneplant, Leadbush, Dried bush | Wooden structures, Concrete structures, Recharging station vault, 0.2.9-Mind-Swap chip site | Contains the 0.2.9-Mind-Swap chip site (Chip 3 of 6) | |
| 5 | 1200–1500m | Subterranean Jungle & Predator Den | 21.8°C | 5.6°C to 31.5°C | Elder thornback (6000 HP apex predator), Tentacle-plants, Skullcrushers, Coils | Elder thornback, Thornback, Tentacle-plant, Overgrown tick, Cave tick, Sand stalker, Shade crawler | Geyser, Jump pad, Spike trap, Bear trap, Cave tick spawner, Skullcrusher, Banana-plant, Coil | Banana-plant, Pop, Sandvine, Glowplant, Stoneplant, Ceiling rye, Geotree, Hydreed, Leadbush | Wooden structures, Brick vault, 0.0.7-Emergency Rejuvenation chip site | Contains the 0.0.7-Emergency Rejuvenation chip site (Chip 4 of 6); final layer of the Steam Demo | |
| 6 | 1500–1800m | Sub-Zero Glacial Cavern | -30.6°C | -33.0°C to -24.0°C | Lethal hypothermia (-30.6°C average), Thin ice collapse, Gunmines, Snow striders, Falling icicles | Snow strider, Shade crawler | Gunmine, Turret, Spike trap, Fan trap, Geyser, Jump pad, Bear trap, Icicle, Ice stalagmite | Frigiant, Heatfern, Glowplant, Stoneplant, Leadbush | Life-pod, Ion space heater | Navigate between Life-pods and Ion space heaters to survive freezing descent to Layer 7 | |
| 7 | 1800–2100m | Rain-Soaked Bioluminescent Mycelium Caves | 17.8°C | 14.2°C to 23.2°C | Constant rain causing wetness hypothermia while sleeping, Radioactive fungi, Grabber-shrooms, Sawblades | Grabber-shroom, Overgrown tick, Cave tick, Shade crawler | Sawblade, Sidestabber, Dropshroom, Bear trap, Jump pad, Cave tick spawner | Fungali bungali (exclusive source of Bunchunks for Procoagulant), Glowshroom, Brownshroom, Bouncecap, Mushroom tree | Life-pod shelters, MINI-AI chip site | Contains the MINI-AI chip site (Chip 5 of 6) | |
| 8 | 2100–2400m | Distorted Crystal Abyss | 18.5°C | 16.9°C to 20.7°C | Sheer vertical drops, Volatile distorted crystals (Turbulent/Blood/Relief/Oxygen/Digestion/Soothing), Flying Manifestations | Manifestation | Crystal hazards, Geyser | None (mineral-only biome; harvest Crystal shards instead) | Crystal formations and deep vertical shafts | High-verticality traversal layer; Jetpack or grappling gear strongly recommended | |
| 9 | 2400–2700m | Magma Tubes & High-Pressure Vents | 20.9°C | 10.7°C to 40.8°C | Extreme heat (up to 40.8°C), Liquid Magma pools, Barotrauma air pressure in lower half, Laser & Cryo Drones | Laser Drone, Cryo Drone | Lava Geyser, Piston, Sawblade, Fan trap, Bear trap, Stalagmite | Coldpuff, Spicevine, Stoneplant | Industrial vents, Kinetic Transmitter chip site | Contains the Kinetic Transmitter chip site (Chip 6 of 6) | |
| 10 | 2700–3000m | Deepest Cargo Vault & High-Pressure Core | 22.0°C | 18.0°C to 26.0°C | Continuously rising air pressure causing lethal Barotrauma, Dense gauntlet of every mechanical trap type | None (pure mechanical trap gauntlet) | Spike trap, Barbed fence, Bear trap, Turret, Ceiling turret, Landmine, Coil, Spent fuel, Sound cannon, Skullcrusher, Sawblade, Piston, Fan trap | Stoneplant | The Cargo structure, High-powered Drill Pod (requires the Cargo to activate) | Never rolls a Layer Modifier; retrieve the Cargo here and board the high-powered Drill Pod (or loop to Layer 1 in Endless mode) | |
| 11 | Ascent to Surface | Fleshy Organic Ascent Shaft | 24.0°C | 20.0°C to 28.0°C | Steep upward climb after the Drill Pod breaks down; managing accumulated trauma before reaching the Surface Lab | None | None | Crimson bush, Crimtree, Pus sack, Vein, Pop, Mushlight, Leadbush, Brownshroom, Ceiling rye, Stoneplant | Broken Drill Pod arrival point, Surface Exit (at top of layer) leading to the Lab / Surface endings | Climb to the top exit carrying the Cargo (or M.E.R.C. scarf in inventory) to trigger Bio-pod, Escape, or Mercenary ending |
In addition to the 11 numbered descent layers, expeditions encounter specialized transition biomes, Training Labs, Trader outposts, and anomalous sub-layers. Filter by entry type below to inspect every documented subterranean zone.
| Zone / Layer Name | Zone Classification | Layer # | Biome & Terrain | Avg. Temp | Primary Environmental Hazards | Hostile Fauna & Turrets | Traps & Obstacles |
|---|---|---|---|---|---|---|---|
| Gravel Lands | Subterranean Layer | 1 | Cavernous Cold Rock & Clay | 15.0°C | Fall damage, Spike traps, Geysers, Shade crawlers | Shade crawler | Geyser, Jump pad, Spike trap |
| Deeper Gravel Lands | Subterranean Layer | 2 | Pitch-Black Flooded Caves | 17.5°C | Total darkness, Groundwater & Lumalgae flooding, Cave tick infestations | Shade crawler, Cave tick | Geyser, Jump pad, Spike trap, Barbed fence, Bear trap, Cave tick spawner |
| Dried Desert | Subterranean Layer | 3 | Arid Sandstone & Viscous Oil Chasms | 26.6°C | Viscous Oil pools (exhaustion drowning), Automated Turrets, Landmines, Tall vertical drops | Shade crawler, Sand stalker | Jump pad, Barbed fence, Bear trap, Turret, Stalactite, Landmine, Waste pipe |
| Wasteland | Subterranean Layer | 4 | Radioactive Industrial Ruins | 25.8°C | Radiation sickness, Radwater pools, Radioactive barrels, Ceiling turrets, Extreme thermal swings | Shade crawler, Cave tick, Sand stalker | Turret, Ceiling turret, Landmine, Barbed fence, Bear trap, Radioactive barrel, Spent fuel, Sound cannon |
| Overgrown Depths | Subterranean Layer | 5 | Subterranean Jungle & Predator Den | 21.8°C | Elder thornback (6000 HP apex predator), Tentacle-plants, Skullcrushers, Coils | Elder thornback, Thornback, Tentacle-plant, Overgrown tick, Cave tick, Sand stalker, Shade crawler | Geyser, Jump pad, Spike trap, Bear trap, Cave tick spawner, Skullcrusher, Banana-plant, Coil |
| Frozen Chasm | Subterranean Layer | 6 | Sub-Zero Glacial Cavern | -30.6°C | Lethal hypothermia (-30.6°C average), Thin ice collapse, Gunmines, Snow striders, Falling icicles | Snow strider, Shade crawler | Gunmine, Turret, Spike trap, Fan trap, Geyser, Jump pad, Bear trap, Icicle, Ice stalagmite |
| Fungal Pools | Subterranean Layer | 7 | Rain-Soaked Bioluminescent Mycelium Caves | 17.8°C | Constant rain causing wetness hypothermia while sleeping, Radioactive fungi, Grabber-shrooms, Sawblades | Grabber-shroom, Overgrown tick, Cave tick, Shade crawler | Sawblade, Sidestabber, Dropshroom, Bear trap, Jump pad, Cave tick spawner |
| Crystalline Hollow | Subterranean Layer | 8 | Distorted Crystal Abyss | 18.5°C | Sheer vertical drops, Volatile distorted crystals (Turbulent/Blood/Relief/Oxygen/Digestion/Soothing), Flying Manifestations | Manifestation | Crystal hazards, Geyser |
| Geothermal Vents | Subterranean Layer | 9 | Magma Tubes & High-Pressure Vents | 20.9°C | Extreme heat (up to 40.8°C), Liquid Magma pools, Barotrauma air pressure in lower half, Laser & Cryo Drones | Laser Drone, Cryo Drone | Lava Geyser, Piston, Sawblade, Fan trap, Bear trap, Stalagmite |
| Where We Must Reach | Subterranean Layer | 10 | Deepest Cargo Vault & High-Pressure Core | 22.0°C | Continuously rising air pressure causing lethal Barotrauma, Dense gauntlet of every mechanical trap type | None (pure mechanical trap gauntlet) | Spike trap, Barbed fence, Bear trap, Turret, Ceiling turret, Landmine, Coil, Spent fuel, Sound cannon, Skullcrusher, Sawblade, Piston, Fan trap |
| Crimson Ascent | Subterranean Layer | 11 | Fleshy Organic Ascent Shaft | 24.0°C | Steep upward climb after the Drill Pod breaks down; managing accumulated trauma before reaching the Surface Lab | None | None |
| Flooded (Layer Modifier) | Layer Modifier | 1 | 40% Base Layer Modifier Roll | Varies | Increased water/fluid pool generation across cavern basins | Standard Layer Pool | Drowning & Wetness hazards |
| Pitch Black / Blackout (Layer Modifier) | Layer Modifier | 2 | 40% Base Layer Modifier Roll | Varies | Suppresses ambient background illumination; requires Flashlight, Headlamp, or Rose light | Standard Layer Pool | Hidden floor traps |
| Solar-Struck (Layer Modifier) | Layer Modifier | 3 | 40% Base Layer Modifier Roll | Varies | Temporarily disables the survivor neural chip (never spawns during a valid Mercenary Ending run) | Standard Layer Pool | HUD telemetry disruption |
| Heavily Trapped (Layer Modifier) | Layer Modifier | 4 | 40% Base Layer Modifier Roll | Varies | Greatly increased density of Landmines, Turrets, Spike traps, and Bear traps | Standard Layer Pool | High trap density |
| Infested (Layer Modifier) | Layer Modifier | 5 | 40% Base Layer Modifier Roll | Varies | Elevated creature and Cave tick spawner density throughout tunnels | Elevated Fauna Spawns | Cave tick spawners |
| Irradiated (Layer Modifier) | Layer Modifier | 6 | 40% Base Layer Modifier Roll | Varies | Additional radioactive barrels and background radiation pockets | Standard Layer Pool | Radioactive barrels |
| Barren / Scarcity (Layer Modifier) | Layer Modifier | 7 | 40% Base Layer Modifier Roll | Varies | Reduced natural flora and crate spawns; forces reliance on carried rations | Standard Layer Pool | Starvation & Dehydration |
High subterranean gravity turns even moderate drops into compound ankle and tibia fractures. Carve stepped ledges with a Makeshift Digging Tool or Machete, deploy ropes or climbing pitons, and keep a Jetpack or Claw Pack equipped when crossing wide chasms.
Upper frozen strata drain core body temperature into Hypothermia, while deep volcanic and desert layers trigger Hyperthermia and rapid dehydration. Carry Campfire components for cold biomes and extra Canteens of sterile water before descending into high-heat strata.
Descending past a layer boundary is one-way. Before exiting Layer 1, 3, 5, 7, or 9, verify Whether the Mercenary questline requires scanning a malfunctioning Tech-Ball, retrieving a data drive, or speaking to the Mercenary NPC on that stratum.