Mortal Shell 2: Crumbling Tunnel Dungeon Walkthrough

The Crumbling Tunnel in Mortal Shell 2 is a short cave with a hard stop at the end. You drop in for a map. The moment you take it, the ceiling starts to fall.

Quick answer: Enter the mist portal by the Proxima Shell in the Shattered Beacon area, ride the elevator down, grab Ventrium and Laterite, shoot the explosive jars for the Triarch Repeater Map, then sprint back to the lift before rock seals the cave.

Crumbling Tunnel location in Mortal Shell 2

Look for a white mist portal in the Shattered Beacon area, next to where you found the Proxima Shell. That opening is the right entrance. Follow the path inside until you reach a wooden lift.

A second place uses the same name in Widow’s Overlook, southwest of Fainweald. That room only holds a Glimpse and a nearby journal. It has no elevator and no cave-in. If you need the map, stay with the Proxima portal.

Ventrium and Laterite in the first chambers

Step through the mist and move into the narrow rock corridor. Keep walking until the wooden elevator platform is in front of you.

Hooded character with a bow walking through a narrow cave corridor — A hooded character moves through the narrow cave corridor past the mist entrance. Image credit: Cold Symmetry / via @SanterSensei

Use the wooden lever on the lift. Ride the platform down the shaft and step off at the bottom.

Crouch through the low gap ahead. A shield-wielding Brigand and two Wretches wait in the next stretch. Clear them before you search the room.

Hooded character approaching a dark cavern opening with health and equipment HUD — The character leaves the lift and heads through the rocky cavern toward a dark opening. Image credit: Cold Symmetry / via @SanterSensei

Search the first chamber for a green statue. Ventrium sits on that statue. Check both sides of the passage if it is not in your line of sight.

Push farther down the tunnel and watch the ceiling. Rocks start to drop here. A Wretch stands in that fall zone. Hit it from range and let the debris finish the job.

Inspect the growth beside the rockfall for Laterite. A large stone may drop near an enemy as you approach. The material is behind that fall.

Item	Where it sits
Ventrium	Green statue in the first chamber after the opening fight
Laterite	Growth beside the rockfall farther down the tunnel
Triarch Repeater Map	Under explosive jars at the end of the dark side cave

Triarch Repeater Map pickup

Do not walk to the far dead end yet. The last stretch is a trap once the map is in your hands. Get the side pickups first, then commit.

Take the dark cave on the left. Follow that path all the way to the blocked end.

Shoot the explosive jars in front of you. The blast clears the pile and leaves a pale object on the floor.

Player aiming a sidearm at a cave target with a Fire Sidearm RT prompt — The player aims a sidearm at the centered target to break the explosive jars. Image credit: Cold Symmetry / via @SanterSensei

Pick up the Triarch Repeater Map. That sheet marks where Proxima’s sidearm can be found later. The cave begins to fail as soon as the map leaves the ground.

Escape the collapsing tunnel

Turn around and run toward the lit stretch and the elevator. Dust and small stones falling from the ceiling mark the next boulder. Move off that line before the rock lands.

Hooded character sprinting through a dark cavern after taking an item — The character sprints back through the dark cavern after taking the map. Image credit: Cold Symmetry / via @SanterSensei

Ignore any enemy that appears on the return path. Stopping to fight is how the rocks catch you. Keep moving.

Reach the wooden elevator platform and ride it up. Leave through the same mist you used to enter.

Hooded character running across a wooden platform toward the cave exit — The character runs across the wooden elevator platform toward the cave exit. Image credit: Cold Symmetry / via @SanterSensei

You are done when the Triarch Repeater Map is in your inventory and the tunnel behind the lift is fully blocked. There is no way back in for missed materials. If you died in the collapse, the pickup did not finish. Run the cave again and leave as soon as the map is taken.