Mortal Shell 2 Crumbling Tunnel Walkthrough

The Crumbling Tunnel is a mid-game area in Mortal Shell 2: The Fallen Temple that connects the Sunken Grotto to the Ashen Citadel. This walkthrough covers every item, enemy ambush, and the correct path to the boss door, including the two hidden side chambers most players miss. You’ll need the Rusted Key from the Grotto’s merchant to open the locked gate at the tunnel’s midpoint.

Prerequisites and Entry

Before you enter the Crumbling Tunnel, make sure you have the Rusted Key (dropped by the Grotto’s merchant after you give him 3 Mossy Tokens) and at least one Lantern Oil for the dark sections. The entrance is a collapsed archway on the north wall of the Sunken Grotto, marked by a broken pillar and a faint blue glow. If you haven’t defeated the Grotto’s mini-boss (the Drowned Brute), the tunnel’s first section will have extra enemies.

Path Through the First Collapsed Section

Enter the tunnel and follow the narrow stone corridor until you reach a large chamber with a collapsed ceiling. The rubble blocks the direct path, so you must climb the broken pillars on the left side. Watch for two Grotto Rats that drop from the ceiling as you climb. At the top of the pillars, cross the wooden beam to the right and drop down to the lower ledge. From here, you’ll see a glowing Quenching Acid on a small alcove—grab it, then continue through the archway on the far side.

Locked Gate and the Rusted Key

The next corridor leads to a locked iron gate. Use the Rusted Key to open it. Behind the gate is a short hallway with a pressure plate in the center. Stepping on the plate triggers a spike trap from the ceiling, so roll immediately after stepping on it. At the end of the hallway, you’ll find a Gland (a key item needed for the boss fight) on a pedestal. Take it, and a cutscene will show the tunnel collapsing behind you, blocking the way back.

Hidden Side Chambers

There are two optional side chambers in the Crumbling Tunnel. The first is a breakable wall just before the locked gate—hit the cracked section to reveal a small room with a Tarspore and a lore note. The second is after the pressure plate hallway: look for a false wall on the right side (it has a slightly different texture). Inside, you’ll find a Weapon Upgrade Material and a shortcut ladder that leads back to the Grotto’s entrance, but it’s blocked until you open it from the other side.

Boss Arena and the Ashen Citadel Exit

After grabbing the Gland, continue forward into a large circular arena. The boss, The Hollow Warden, will awaken when you approach the center. Defeat it (dodge its overhead slam and punish after the third hit of its combo). Once it’s dead, the exit to the Ashen Citadel opens on the far side. Before leaving, search the arena’s edges for a Glimmering Fragment and a Healing Balm.

Common Mistakes and Tips

• Missing the Rusted Key: If you didn’t buy it from the Grotto’s merchant, you’ll be stuck at the iron gate. You can backtrack to the Grotto, but the tunnel collapses after you take the Gland, so make sure you have it before that point.
• Triggering the spike trap: The pressure plate is easy to miss. Always roll immediately after stepping on it, or you’ll take heavy damage.
• Not breaking the false wall: The second hidden chamber is easy to miss because the wall texture is subtle. Use a heavy attack to break it.
• Falling into the pit: In the first collapsed section, there’s a gap in the floor near the wooden beam. Hug the right side to avoid falling.

Item Checklist

• Quenching Acid (first section alcove)
• Gland (required for boss)
• Tarspore (hidden chamber #1)
• Lore note (hidden chamber #1)
• Weapon Upgrade Material (hidden chamber #2)
• Glimmering Fragment (boss arena)
• Healing Balm (boss arena)

Frequently Asked Questions

What happens if I miss the Rusted Key?

You can still go back to the Sunken Grotto to buy it from the merchant, but only before you take the Gland. Once you pick up the Gland, the tunnel collapses behind you, and the way back is blocked. So make sure you have the key before entering the locked gate area.

Can I return to the Crumbling Tunnel after leaving?

Yes, after you defeat the boss and exit to the Ashen Citadel, you can return through the shortcut ladder (if you opened it) or by backtracking from the Ashen Citadel. However, the tunnel’s first section remains collapsed, so you can’t reach the Grotto from that side anymore.

How do I open the shortcut ladder?

The shortcut ladder is in the second hidden chamber. To open it, you need to pull the lever on the wall inside that chamber. This will lower the ladder, allowing you to climb up to the Grotto’s entrance area. It’s a one-way shortcut that helps you return to earlier areas quickly.

Is the Hollow Warden boss optional?

No, the Hollow Warden is a required boss. You must defeat it to progress to the Ashen Citadel and continue the main story. There are no optional bosses in this area, but the two hidden chambers are optional.

What level should I be for the Crumbling Tunnel?

It’s recommended to be at least level 20 with a +3 weapon. The enemies here hit hard, and the boss has a large health pool. If you’re struggling, consider upgrading your weapon with the Quenching Acid you find in the tunnel and using Tarspores to increase your damage.

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