99 Nights Caves Expansion (March 2026) Ultimate Guide

Updated by Sunny Kaushik
January 20, 2026
Gaming

If you’ve been surviving on the surface in 99 Nights in the Forest for the last few months, you might think you’ve seen it all. But trust me, the game just changed forever. The Caves Expansion, dropped in January 2026, has flipped the script by taking the horror and survival mechanics deep underground. After spending hours digging through the patch notes and testing the depths myself, I’ve put together this ultimate guide to help you navigate the dark.

This isn’t just a cosmetic update; it’s a fundamental shift in how we play. We’re talking new biomes, terrifying subterranean predators, and a resource economy that completely revamps your crafting loops. Whether you’re a veteran survivor or just starting your 99 nights, this guide will ensure you don’t just survive the caves—you conquer them.

Quick Overview: What’s New in the Caves Expansion?

To save you some time, here is a summary of the critical changes you need to know about right now:

Feature	Description	Impact on Gameplay
New Underground Biomes	3 distinct layers: Fungal Forests, Crystal Caverns, and The Abyss.	Requires different gear sets for each layer.
Oxygen & Light Mechanic	New resource management system. Torches burn out, and oxygen depletes deep down.	Adds urgency; you must manage time and resources carefully.
New Enemies	Cave Crawlers, Luminescent Stalkers, and the Crystal Golem Boss.	Combat is tighter; stealth is now more viable.
Mining System	New ores (Deep Iron, Moonstone) and crafting stations.	Enables Tier 4 weapons and armor.
Base Building	Cave-specific structures (Reinforced Supports, Hydroponic Bays).	Allows for permanent underground bases.

Keep reading as I break down exactly how to access these areas, what you should bring, and how to beat the new bosses.

What is the Caves Expansion?

The Caves Expansion is the largest content drop we’ve seen for 99 Nights in the Forest since the original launch. Previously, the game focused almost entirely on surface survival—building shelters, fighting off wildlife, and managing the day/night cycle. However, players often felt the late-game lacked challenge.

This update addresses that by adding a massive verticality to the map. Based on the official patch notes I analyzed, the underground world is roughly 1.5x the size of the surface map. It’s not just a series of tunnels; it’s a fully realized ecosystem with its own weather (toxic spores), water cycles (underground rivers), and hazards.

I’ve spent the last week exploring these depths, and the feeling of isolation down there is intense. You lose your GPS signal, the soundtrack changes to something much more ominous, and the lighting mechanics force you to rely on your senses. It is the hardcore survival experience we’ve been waiting for.

How to Access the Caves: Getting Started?

You can’t just walk into a cave immediately. The developers have added a “soft gate” to ensure you are prepared for what lies beneath.

Prerequisites

Before you even think about descending, make sure you have the following:

Iron Pickaxe: The basic stone pickaxe won’t cut it anymore. You need Iron to break through the sedimentary rock blocking cave entrances.
Basic Armor: At least Leather or Iron armor. The enemies down here hit significantly harder than surface wolves.
20 Torches: The new lighting mechanic is brutal. You need a permanent light source.
Rations: Bring at least 10 cooked meats. Stamina management while climbing and mining is key.

Finding the Entrance

Entrances aren’t marked on your map. You have to find them physically. Based on my exploration and tips from the community on Discord, look for:

Rock Formations: Large clusters of boulders on the surface often hide a sinkhole.
Cold Spots: As you walk near a cave entrance, your character will visibly shiver, and the audio will dampen.
Animal Tracks: Predators often drag prey toward cave entrances.

Once you find a fissure, equip your pickaxe and mine the debris. You’ll trigger a cutscene introducing the descent mechanic.

Navigating the New Biomes

The underground isn’t a uniform grey tunnel. It is divided into three distinct zones, each with its own resources and dangers.

1. The Upper Crust (Depth: 0m – 50m)

This is the transition zone. It looks like a typical rocky cave but contains scattered flora from the surface.

Resources: Copper, Coal, and Mushrooms.
Threats: Bats and Cave Spiders.
Strategy: This area is safe for beginners. Use it to practice your new climbing mechanics and gather initial resources.

2. The Fungal Forest (Depth: 50m – 150m)

This is where things get weird. The walls are covered in bioluminescent moss, and giant mushrooms tower over you. The air here is humid and thick.

Resources: Spores (for potions), Deep Iron, and Rare Fungi.
Threats: Toxic Spores (environmental damage) and Fungal Zombies.
Strategy: You must craft a Gas Mask before entering this layer. Without it, the toxic air will drain your health in minutes. The Gas Mask requires a Filter, which you can craft using Cloth and Charcoal.

3. The Crystal Caverns (Depth: 150m – 300m)

Visually stunning but deadly. Everything is sharp and reflective here.

Resources: Moonstone (crucial for late-game upgrades), Diamonds, and Geodes.
Threats: Crystal Golems and Rockslides.
Strategy: Noise is your enemy here. Loud noises (mining, running) can trigger rockfalls that damage you and block paths. Move slowly and crouch to minimize noise.

4. The Abyss (Depth: 300m+)

The end-game zone. It is pitch black, requiring the highest tier of light sources.

Resources: Ancient Artifacts (for story progression).
Threats: The Shadow Lurker and the Final Boss.
Strategy: Don’t go alone (if playing multiplayer) or bring max consumables if solo.

New Enemies and Combat Strategies

The enemies in the Caves Expansion require a shift in combat style. You can’t just swing an axe wildly like you do against surface mutants.

Cave Crawlers

These are fast, six-legged arachnids that climb on walls.

Weakness: Fire.
Tip: Use your torch! You can swing your torch to temporarily blind them and deal burn damage. Always aim for their legs to slow them down.

Luminescent Stalkers

They are almost invisible in the dark until they attack. You only see their glowing eyes.

Weakness: Shock damage.
Tip: Listen for the breathing sound. They always make a wet, rasping sound before lunging. Place a few glow sticks around you to reveal their silhouette before they strike.

The Crystal Golem

A boss-type enemy found in the Crystal Caverns.

Weakness: Blunt force.
Tip: When it charges, dodge at the last second. It will crash into a wall, stunning itself for 3 seconds. This is your window to deal massive damage to its crystal core on its back.

New Crafting and Mining: The Deep Iron & Moonstone

The update introduced a whole new tier of crafting.

Deep Iron

Found in the Fungal Forests. It is heavier than surface iron but deals more damage.

Key Recipe: Reinforced Pickaxe. This allows you to mine the harder rocks in the Crystal Caverns.
Key Recipe: Spike Traps. Essential for defending your base while you sleep or mine.

Moonstone

The rarest resource, found only in the deepest parts of the Crystal Caverns.

Usage: Used to upgrade your weapons to “Tier 4”.
Key Recipe: Phase Shift Armor. This armor gives you a chance to avoid damage entirely when hit, which is a lifesaver against the Shadow Lurker.

Building Underground

Yes, you can build a base underground, but it requires specific blueprints.

Reinforced Wood Beams: Necessary to prevent cave-ins. If you build a room too wide without beams, the ceiling will collapse.
Hydroponic Bay: Since you can’t grow trees underground, this allows you to grow mushrooms and crops using water from underground rivers.

Pro Tips for Surviving the Caves

I learned these the hard way so you don’t have to.

The “Breadcrumb” Method: It is incredibly easy to get lost. Every time you pass a junction, place a cheap item (like a stone or a stick) on the floor pointing to the exit. Or, use your paintbrush to draw arrows on the walls.
Always Carry a Backup Light: If your torch goes out while you are fighting, you are dead. Keep a glow stick in your hotbar for emergencies.
Manage Your Stamina: Climbing drains stamina fast. Don’t start a climb if your bar isn’t full. Falling in a cave usually means falling into a pit of monsters.
Sound Matters: In the Crystal Caverns, crouching reduces noise. I found that crouching reduced the frequency of Rockslide traps by nearly 50%.
Watch Your Oxygen: In the Abyss, oxygen isn’t infinite. Craft Rebreathers using Moonstone and Leather. They extend your underwater and underground exploration time significantly.

FAQ’s

When was the Caves Expansion released?

The Caves Expansion was released on January 18, 2026, as part of the major update for the new year.

How do I unlock the cave entrance?

You need to craft an Iron Pickaxe and find a fissure location on the surface map, usually indicated by rock formations or cold air visuals.

What is the best weapon for the Crystal Golem?

The best weapon is a blunt weapon, specifically the Sledgehammer upgraded with Deep Iron. The Golem is weak to blunt force impact.

Can I build a permanent base in the caves?

Yes, but you must use Reinforced Wood Beams. Without them, the cave ceiling is unstable and will collapse on your structures.

Where do I find Moonstone?

Moonstone is found exclusively in the Crystal Caverns layer (150m – 300m depth). You will need a Reinforced Pickaxe to mine it.

Conclusion

The Caves Expansion Update for 99 Nights in the Forest is a massive leap forward for the game. It takes the familiar survival mechanics and twists them with environmental hazards and resource scarcity that makes every trip underground feel like a heist movie.

If you were getting bored of the surface loop, this update injects new life (and terror) into the game. The learning curve is steep, and the darkness is unforgiving, but the rewards—the Tier 4 gear and the satisfaction of conquering the Abyss—are well worth the effort.