Mortal Shell II Dungeon Guide: Every Dungeon
A Mortal Shell II dungeon guide covering step-by-step routes through Holding Cells and Thieves Retreat, plus every other dungeon's location and loot.
Mortal Shell II scatters more than thirty dungeons across its open world, and almost all of them are optional side content you stumble into through wells, hidden doors, and enemy camps rather than the critical path. This guide walks through the two dungeons with confirmed, detailed routes — Holding Cells and Thieves Retreat — then lists where every other known dungeon sits and what it pays out.
How Dungeons Fit Into the Game
Dungeons here are self-contained pockets off the main map, usually gated by a key, a boss fight, or a puzzle solved from outside. Most reward a specific weapon, a Shell upgrade stone, or gold and Ventrium, so they're worth the detour even off the main path. Entrances vary on purpose — a well in a hamlet, an elevator near a beacon, a gap in a rock wall — so keep an eye out as you explore.
Holding Cells: Step-by-Step Walkthrough
Holding Cells sits inside Blackridge Hamlet, reached by dropping down the well at the center of the settlement.
- Cross the main bridge leading into the larger interior structure.
- Break the illusionary wall on the left of the bridge to expose a secret area.
- Climb the walkway and scaffolding up to a closed gate blocking the way forward.
- Beat the Armed Knave guarding the entrance ahead, wielding a Halberd.
- Flip the hidden switch behind boxes near a gloom tree to open that gate.
- Clear the ambushed soldiers past the gate, hit by an arrow trap.
- Break a second illusionary wall at the end of the hall to trigger a fight against three armored enemies.
- Choose an exit: a secret path warps you to the outskirts of the Citadel of Penance, or a lift drops you to the lower level.
- Push through the lower level, thick with creature enemies you can mostly bypass.
- Take the second lift up into an arena, grabbing a Glimpse at the top first.
- Enter the arena to trigger the Rabid Grisha Pack boss fight.
Don't try to block the Grisha's grab
The Rabid Grisha Pack's red-glowing lunge grab bypasses Harden — dodge it, don't block. Shoot the two overhead cylinders when a Grisha stands under one to drop and stun it, turning the fight into a 1-on-1. Parrying a normal claw swipe grants full invincibility on the riposte. Clearing the fight drops the Inflamed Clawstone.
Player footage also describes a lower route: a Feeding Room Key in a cabin near poison enemies and bats unlocks a boss door to the same two-enemy fight (called "Gishes" there, likely the Grisha under another name) with the same Clawstone drop. It's unconfirmed whether that's a second door into the same arena or a distinct fight, so treat it as an alternate route rather than a separate boss.
Beyond Holding Cells: Martyr's Prison and the Great Martyr's Blade
Holding Cells connects to Martyr's Prison, home of the Great Martyr's Blade — valued for its two-stage sprinting heavy attack and its ability to interrupt attacks the starting Iconoclast sword can't stop. Reaching it needs Mether's Breath, unlocked by turning in around 10 Ova at the Gloom Siphon in Marrow Keep. Inside the prison, you break out of one cell while clearing enemies, then hit a plate in a second cell to open the final arena: three "Lanky" abominations and one large enemy. Kill a Lanky fast, dodge the large enemy's telegraphed rolling charge while mopping up the rest, then bait its exposed thorns before finishing it. The treasure room beyond holds the Great Martyr's Blade, already at level 4.
Thieves Retreat: Step-by-Step Walkthrough
Thieves Retreat sits just north of the Nochtean Gate Beacon. It centers on an invisible floor spanning a destroyed bridge, patrolled by lightning-casting ghosts, over a monster-filled pit.
- Find the entrance by heading north from the beacon through arched doorways, dropping past a hostile Stoner, and entering the archway opposite it.
- Gear up first — the ghosts' lightning spells can't be blocked.
- Trace the invisible path: follow the faint outline along the bridge's ledges and the floating corpses toward the two lit torches at the exit.
- Fight offensively, since the invisible floor leaves almost no room to maneuver.
- Recover from a fall by clearing or luring monsters off the lever that runs the elevator back up.
- Grab the Revered Gland at the far end, surrounded by statues, to open a return portal.
Gear check before the invisible floor
Give Proxima two levels in Ampereon for Lightning resistance and immunity, and slot the Galvanic Shard passive for more. Her Biosampler ability also helps by pulling ghosts in close on a floor with no room to kite.
There's a Ventrium totem near a shack in the pit, and a second invisible floor near the entrance's left side leading to a trap-and-enemy hallway. Resolve roots appear in both spots, hinting at secrets tied to Shell abilities — that link isn't confirmed, so treat it as unconfirmed.
Every Other Dungeon on the Main Route
- Shrine of Trials: Mushroom Village, needs the Chapel Key; rewards the Axe and Dagger.
- Martyr's Tomb: Near Widow's Overlook, past the Great Arbiter of Flesh; rewards the Parasitic Stone.
- Flooded Village: Down a bridge near Blackridge Pass Beacon; rewards the Forgotten Crossbow.
- Coward's Retreat: Right of the Blackridge Pass ramp; yields extra gold.
- King's Crypt: Left of the Crumbling Tunnel exit, trap-heavy; rewards the Veteran's Battle Axe.
- Feeding Grounds: Behind a chapel, needs all Golden Tombstones in Stones of Remembrance; rewards the Myriad's Stone.
- Overrun Quarry: Near Stones of Remembrance; rewards roughly 2,000 gold.
- Ravaged Hideout: Unlocked after the Bloodcursed Lithopod boss; contains the Salvaged Trebuchaxe.
- Illusionist's Cache: Near Desolate Peak, needs the Crypt Key; rewards the Shuddering Stone.
- Disciple's Stash: Hag's Path, behind a wooden wall; rewards 5 Ventrium.
- Waterfall Camp: Ruins of Nochte; rewards a Coin of Mammon and a Ventrium.
- Ravaged Tomb: Elevator near the Nochtean Gate Beacon; contains the Duality Stone.
- Central Sewers (Slumwater Drain): Rewards Ironpiercer's Stone.
- Central Sewers (Executioner's Pulpit): Leads to the Tishina's Confessor miniboss.
- Smuggler's Hideout: Outskirts of Mammon, behind an enemy camp; rewards a Coin of Mammon.
- Hag's Pit: Outskirts of Mammon, near a Corrupted Statue; rewards coins, Laterites, and Burnt Effigies.
Full Dungeon Name Index
The wider name list cross-referenced across guides adds: Bellkeeper's Corner, Besieged Ruins, Blackwell Cavern, Chamber of Becoming, Collapsed Mine, Crumbling Tunnel, Deserted Mine, Desolate Keep, Garrick's Den, Grisha Hunting Grounds, Hall of Echoes, Hall of Murmurs, Obsidianite Mines, Parasitic Stash, Revenant Graves, Revered Dungeon, Ritual Grounds, and Sentry's Grave. Some of these, including Chamber of Becoming and Ritual Grounds, don't have a published walkthrough yet — their layouts and rewards are still TBD.