Updated August 25, 2026
Laboratory X16 is the most important mission in S.T.A.L.K.E.R. 2: Cost of Hope. It's where you'll solve the DLC's biggest puzzles, unlock one of its best armor sets, fight the Pseudobrain, and make the only choice that permanently locks the Duty or Freedom ending.
Many guides treat X16 as a simple mission walkthrough, but that misses the parts players actually get stuck on: Should you follow Mavka or Zulu? Where is the X16 key card? What's the 1408 keypad code? How do you solve the projector puzzle? And where should you make your manual save?
This guide covers the entire laboratory from entry to escape, including every major puzzle, secret loot, boss strategy, and the real point of no return.
📋 Table of Contents
- How to Start Laboratory X16
- Should You Choose Mavka or Zulu?
- Mavka Route: X16 Key Card
- Zulu Route: Explosives
- Entering Laboratory X16
- Restore Power Puzzle
- Keypad Code (1408)
- Projector Puzzle & Safe Code
- Brummbar Exoskeleton Secret
- Hidden RPG Room
- The Real Duty or Freedom Choice
- Pseudobrain & Nord Boss Guide
- How to Escape X16
- Best Manual Save Point
- Hidden Loot Checklist
- FAQ
- Community Tips
How to Start Laboratory X16
Laboratory X16 is part of the main mission The Destructive Power of the Mind.
Before the mission appears, complete both investigation quests:
- Shadows of the Past
- To the Origins of Freedom
Once both storylines are finished, Mavka and Zulu gather at the Secret Camp and prepare their assault on X16.
Bring before entering:
- A reliable assault rifle
- A shotgun for close quarters
- Plenty of medkits and bandages
- Radiation protection
- At least one free manual save slot
X16 is a long mission with several difficult combat encounters, so repairing your favorite weapons beforehand is well worth it.
Should You Choose Mavka or Zulu?
This is the biggest misconception in the DLC.
The first Mavka/Zulu choice does NOT lock your ending. It only changes how you enter Laboratory X16 and which early unique weapon you receive.
Ending locked? No.
The permanent faction decision happens much later inside the laboratory.
Tip: Choose the route with the weapon you want. You can still switch factions later.
Mavka Route: How to Get the X16 Key Card
If you side with Mavka at the Secret Camp, you'll infiltrate X16 through a quieter side entrance.
Step-by-step:
- Travel to Tunnel Under Lake.
- Defeat or bypass the mercenary squad.
- Search Fire's body for the X16 Key Card.
- Return to the Agricultural Workshop.
- Speak with Mavka.
- Enter the Yantar Production Complex using the card.
Don't waste time clearing every enemy: The mission only requires the key card. Once you've secured it (or Zen confirms he has it during the alternate objective), return immediately instead of hunting every remaining mercenary.
Zulu Route: How to Get the Explosives
Zulu prefers a direct assault on Laboratory X16.
Step-by-step:
- Visit the Old Barracks.
- Find Lyokha Spade.
- Obtain the C-4 explosives.
- Return to Zulu.
- Begin the assault.
You have two ways to obtain the explosives:
Paying is quicker, while fighting saves your money. Neither option changes the story.
Entering Laboratory X16
Although the opening differs, both routes quickly converge inside the same underground laboratory.
You'll fight through:
- Mercenary checkpoints
- Cafeteria
- Morgue
- Living quarters
- Operating theater
- Central research rooms
This is where the puzzles begin.
Restore Power Puzzle
One of X16's most common progression blockers happens after reaching the sealed laboratory door.
Many players assume they're missing another key card. They're not. The problem is the electricity.
Solution:
- Ignore the locked door.
- Follow the objective into the maintenance area.
- Find the electrical control room.
- Activate the power system.
- Return to the sealed corridor.
Once power is restored, the laboratory systems come back online and progression resumes.
X16 Keypad Code (1408)
After restoring electricity, you'll reach a keypad protecting the next section of the laboratory.
Laboratory X16 progression code:
Enter 1408 to unlock the route into the central laboratory.
Important: This keypad is different from the laboratory safe. The safe uses another six-digit code later in the mission.
Projector Puzzle & Safe Code
The operating theater hides X16's best optional reward. Instead of simply entering the safe code, you can actually solve the puzzle in-game.
Where to find the projector slides:
- Research room near the large 3 painted wall.
- Office desk in the same laboratory wing.
- Electroshock chair inside the skeleton cage.
After collecting them, return to the projector in the operating theater and cycle through the images.
Laboratory X16 safe code: The projected images reveal the six-digit combination.
The code combines the markings from the relevant projector slides into 17-10-08.
Brummbar Exoskeleton Secret
Opening the safe rewards one of the strongest armor sets in the DLC.
Reward: Brummbar Exoskeleton, Healing supplies, Ammunition, Consumables.
The Brummbar initially prevents sprinting, but later upgrades unlock full mobility along with additional lead containers for safer artifact use.
Don't leave X16 before opening this safe. It's one of the laboratory's most valuable optional rewards.
Hidden RPG Room
This is the easiest secret to miss.
After obtaining the second projector slide, look for a cracked wall near the barracks. Destroy it with explosives to reveal a hidden room.
Loot inside:
- RPG-7U
- PG-7V Rocket
- Extra ammunition
It's entirely optional, making it one of the best hidden loot rooms in Laboratory X16.
The Real Duty or Freedom Choice
This is the section that matters.
After reaching the upper laboratory, Mavka and Zulu discover Nord's technology and begin arguing over its future. THIS is the permanent faction split.
Make your manual save here: Create a manual save before selecting either dialogue.
Best manual save point: Save immediately before speaking to Mavka or Zulu in the central laboratory. Reloading this save lets you experience both endings without replaying the entire DLC.
Unlike the Secret Camp briefing, this decision cannot be reversed without loading an earlier save.
For the full consequences, see our Missables Before Choosing Duty or Freedom guide.
Pseudobrain & Nord Boss Guide
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The final battle inside X16 has two parts: Nord and the Pseudobrain.
Phase 1 — Clear the mercenaries: Don't immediately focus on the Brain. The mercenaries can overwhelm you while you're trying to shoot the rotating fuses, so eliminate nearby enemies first.
Phase 2 — Destroy the rotating fuses: The Brain is protected by rotating yellow fuses across four levels.
Strategy:
- Shoot every visible fuse.
- Use stairs and moving platforms between floors.
- On Level 3, press the bridge button to create the final path.
- Destroy the remaining Brain cables.
Once the last fuse is destroyed, the Pseudobrain collapses and the laboratory begins to fail.
How to Escape X16
The mission isn't over after the boss.
As you retreat through the tunnels, you'll encounter dangerous environmental anomalies.
Watch for:
- Vortex anomalies
- Glass Shard anomalies
Avoid sprinting blindly through the escape tunnels. The route is mostly linear, but careless movement can still kill you.
After reaching the surface, you'll immediately join your chosen faction in one final firefight before completing The Destructive Power of the Mind.
Best Manual Save Point
If your goal is 100% completion, this is the save you should keep.
Save here, not earlier: Central Laboratory, immediately before the Mavka/Zulu dialogue.
Why here?
- Unlocks both endings
- Lets you obtain both faction weapon routes
- Avoids replaying the entire expansion
This save also pairs perfectly with our Best Faction Weapons — Duty vs Freedom Rewards guide.
Hidden Loot Checklist
- ☐ 1408 keypad opened
- ☐ All projector slides collected
- ☐ 171008 safe opened
- ☐ Brummbar Exoskeleton obtained
- ☐ Hidden RPG room looted
- ☐ Manual save created before the faction choice
FAQ
Does choosing Mavka at the Secret Camp lock the Freedom ending?
No. The first choice only changes your X16 entry route and early weapon reward. The permanent faction choice happens later inside the laboratory.
What is the X16 keypad code?
The progression keypad code is 1408.
What is the Laboratory X16 safe code?
The optional safe uses 171008, which is revealed through the projector-slide puzzle.
Where is the Brummbar Exoskeleton?
It's inside the optional safe in the operating theater's central laboratory wing.
Should I choose Mavka or Zulu?
Choose based on the weapon you want during the assault. You can still switch factions later because the first choice isn't permanent.
Where should I make a manual save?
Immediately before speaking to Mavka or Zulu in the central laboratory. That's the real point of no return.
Community Tips
Before entering X16, repair your favorite weapons, travel light, and keep one dedicated save slot free. During the mission, don't confuse the 1408 progression keypad with the 171008 safe, and don't leave the operating theater without opening the Brummbar Exoskeleton safe.
Most importantly, remember that the Secret Camp decision is tactical—but the conversation inside Laboratory X16 is permanent. That's the moment to create your branch save if you want to experience both the Duty and Freedom storylines.
Guide for S.T.A.L.K.E.R. 2 – Cost of Hope
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