Casualties: Unknown Multiplayer Guide: Setup, Co-op Rules, and Survival

Delving into the subterranean abyss alone is terrifying enough, but experiencing Casualties: Unknown multiplayer elevates the tension to absolute chaos. Thanks to the community-crafted "Casualties: Together" modification, survivors can finally band together to scavenge resources, perform field surgery, and inevitably suffer alongside one another. Getting Casualties: Unknown multiplayer configured properly requires a solid grasp of file installations, host console commands, and the brutal co-op medical mechanics that determine whether your team thrives or perishes in the dark.

Whether you are organizing a squad through Steam lobbies or trying to keep your comrades alive through sudden strokes and radiation sickness, this comprehensive guide covers everything you need to know.

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How to Install Casualties: Unknown Multiplayer (Casualties: Together)

Because the base title is primarily developed as a single-player horror-survival simulator, running co-op requires the community mod called Casualties: Together (developed by creaturefeaturelarry and original creator Krokosha666). The mod integrates cleanly with BepInEx, a widely trusted Unity modding framework.

Step-by-Step Installation Process

1. Locate Your Game Files: Open your Steam library, right-click the title, and select Manage > Browse local files to open the root installation folder directly from the Steam Desktop Client.
2. Install BepInEx: Download the latest release of BepInEx compatible with the game's architecture (typically x64). Extract the contents directly into the game's root directory so that BepInEx.dll and its supporting subfolders sit next to the main executable.
3. Deploy the Multiplayer Mod: Download the Casualties: Together release archive (MPMod.zip). Open the contained mod folder and drag all included files into your root game directory.
4. Launch Through Steam: Start the game via your Steam Library to trigger BepInEx loading. If Steam lobbies do not populate, ensure you are running the game directly through Steam rather than a raw desktop shortcut.

Linux and Steam Deck Configuration

If you are running the game on Linux or a Steam Deck via Proton, you must instruct the compatibility layer to hook into BepInEx's custom DLL files. Right-click the game in Steam, open Properties, navigate to the General tab, and enter the following into the Launch Options field:

WINEDLLOVERRIDES="winhttp=n,b" %command%

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Core Co-op Mechanics and Team Interactions

Playing Casualties: Unknown multiplayer changes fundamental survival dynamics. You are no longer managing only your own vitals; you are actively responsible for keeping your expedition partners breathing. The mod introduces proximity voice chat, physical interaction menus, and temperature sharing to encourage tactical teamwork.

Context Interactions and Player Menus

Right-clicking on an ally opens a contextual interaction menu that grants full access to their physiological status and equipment. This mechanic is vital during high-stress encounters:

• Inspect Health Panel: Examine your teammate's blood pressure, heart rate, oxygen levels, and active traumas.
• Triage and Direct Treatment: Apply bandages, inject medications, set fractured bones, or use advanced tools directly on a wounded partner.
• Inventory Access: Forcibly retrieve items from a downed teammate's bag or deposit emergency medical supplies into their slots.
• Force Feeding: Administer food, water, or medicinal solutions directly into another player's mouth if they are incapacitated.

Shared Survival Features

The mod modifies several single-player parameters to accommodate multiple explorers. Sleeping is disabled by default (EnableSleep rule set to false), and baseline hunger and thirst depletion rates are slowed down so players do not constantly starve while waiting for their party.

Additionally, standing in close proximity allows survivors to share body temperature, preventing hypothermia in freezing biomes. If an explorer is knocked unconscious, surviving teammates can carry them across dangerous terrain rather than leaving them behind.

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Host Server Rules and Console Commands

The host of a Casualties: Unknown multiplayer session possesses comprehensive control over session difficulty, PvP mechanics, and game flow through the in-game console. Modifying these rules allows you to tune the challenge from a forgiving co-op expedition to an unforgiving survival gauntlet.

To adjust session parameters, the host must first activate cheat permissions in the console:

rule sv_cheats 1

If the host wishes to grant admin authority to another client in the room, they can run adminpriv [playername] or share an administrative session password. Every rule modification follows the format rule [rulename] [value].

Handling Player Casualties and Cannibalism

In standard settings, dead explorers enter a spectator camera mode. When the surviving members reach the elevator or end of the current subterranean layer, deceased players automatically respawn. Alternatively, squads can purchase revives directly from underground traders.

However, if supplies run dry, the mod features macabre resource management: players can harvest meat and limbs from deceased comrades to cook over campfires. If the host enables CanAmputateHealthyPlayers, players can even surgically detach limbs from living teammates to stave off starvation during desperate runs.

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Medical Triage: Surviving Traumas, Heart Rates, and Radiation

Medical emergencies in Casualties: Unknown multiplayer develop rapidly and cascade out of control if your squad lacks a designated medic. With complex bodily systems tracking everything from brain integrity to vascular pressure, knowing how to stabilize critical conditions is paramount.

Critical Patient Status Check
 ├── Cardiac Emergency? (BPM > 200 or Fibrillation)
 │    ├── Deploy AED (Check battery charge)
 │    ├── Attach Auto Pump
 │    └── Inject Epinephrine
 ├── Neurological Event? (Integrity Drop / Vision Loss)
 │    ├── Administer Neuro Booster / Brain Grow
 │    └── Check Blood Pressure (Avoid hypertensive crisis)
 └── Environmental Hazard? (Radiation / Poison)
      ├── Move off Toxic Ground / Spent Fuel
      └── Dose with Anti-Rad & Apply Decontamination

Heart Complications and Resuscitation

A recurring danger during heavy combat or physical strain is cardiac arrhythmia. When a character's heart rate spikes past 250 BPM, they frequently enter ventricular fibrillation, leading to swift respiratory collapse.

Field medics should carry an automated external defibrillator (AED) and an Auto Pump. Community reports show that defibrillation has a variable success rate per shock, requiring teams to swap AED batteries and cycle chest compressions until the patient stabilizes.

Brain Bleeds and Neurological Traumas

Player experiences highlight sudden neurological events during prolonged multiplayer sessions. When players trip wire traps, suffer explosive concussions, or endure extreme hypertension, brain integrity can drop rapidly.

If a teammate reports fading vision, flashing vitals, or slurred voice chat, they are likely suffering from a brain bleed or stroke. Immediate administration of a Neuro Booster or Brain Grow compound is necessary to halt neural degradation before permanent death occurs.

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Navigating Layers and Descent Mechanics

Surviving the journey between underground sectors requires strict coordination. The descent elevator and DrillPod structures enforce progression thresholds governed by the host's rules.

By default, the LayerFinishConditionPlayerPercent rule requires at least 50% of the expedition party to arrive at the end gate before the host is prompted to descend. Any stragglers left behind when the timer expires will succumb to environmental hazards or toxic gas, requiring respawns on the subsequent floor.

When entering a DrillPod sequence, every single active survivor must physically board the capsule to proceed. Maintaining open voice channels and clearing landmines or automatic turrets ahead of the squad prevents disastrous last-second wipes right outside the extraction pod.

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Troubleshooting Multiplayer Glitches and Stability

Because the multiplayer mod operates without centralized server infrastructure or client prediction, network stability depends on the host's internet connection and processing capability. Community playtesters frequently encounter physics anomalies, terrain clipping, and desynchronization during large sessions.

• Spawning Inside Geometry: If players spawn wedged inside rock faces or floor tiles on a new layer, surrounding players must use digging tools (like pickaxes) to excavate the trapped survivor's collision box.
• Persistent Audio Alarms: If heart-monitor alarms continue blaring after a patient has been stabilized, cycling the medical interface or having the affected player disconnect and rejoin via the Steam lobby resets the sound loop.
• Severe Framerate Drops: Excessive loose items, unharvested corpses, or uncapped player counts in custom sandbox tests can degrade framerates below 30 FPS. Keep party sizes between 2 and 6 players for optimal synchronization.
• Invisible Inventory Objects: If a traded item (such as blood crystals or medicine) does not render in a recipient's bag, drop the item on the terrain and pick it up manually to re-sync server ownership.

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Frequently Asked Questions

Can you play Casualties: Unknown multiplayer natively without mods?

No. The official base release does not feature native online co-op. You must install the community-made "Casualties: Together" mod alongside the BepInEx framework to host and join multiplayer lobbies.

How many players can join a Casualties: Unknown multiplayer lobby?

While the host console can technically uncap lobbies to large numbers, the recommended group size for Casualties: Unknown multiplayer is 2 to 4 players. Sessions exceeding 6 players often encounter desynchronization, audio bugs, and terrain clipping.

What happens when you die in multiplayer?

By default, deceased players enter spectator mode and automatically respawn once the surviving members successfully transition to the next layer. If the host has enabled the Permadeath console rule, dead players cannot respawn unless revived at an underground trader.

Why is my character's speech slurred in voice chat?

In Casualties: Unknown multiplayer, text chat and proximity voice chat are tied directly to your character's physiological status. If your character suffers lung punctures, severe brain damage, or vocal cord trauma, the mod applies real-time audio filters and text scrambling to simulate the injury.