Mortal Shell 2: How to Unlock Every Secret Dungeon, Hidden Vendor, and Boss Item

Mortal Shell 2 tucks some of its strongest rewards behind illusory walls, world puzzles, and a merchant who only appears after dark. The hidden content covered here includes two secret dungeons, a night-only vendor, a sealed endgame door, and the Seedbearer’s Scripture, an item that weakens the final boss. Each one has an exact trigger, so you can unlock them without guesswork.

Quick answer: Break the illusory wall behind the bookcase in Castigator’s Keep for the Alchemist’s Workshop; take the Slayer Seal from Marrow Keep’s throne (do not equip it) and break four chains in the training room to reach Desolate Keep; light the Gloombound Flame at Marrow Keep to enable Night Mode and find the Collector at the Abandoned Outpost; and collect three glands, then offer them at the Forgotten Tower for the Seedbearer’s Scripture.

Alchemist’s Workshop and the Clockwork Shardstone

This dungeon sits on the wooden platforms below Castigator’s Keep. The fastest route is to fast travel to the Castigator’s Keep beacon and work your way down toward the southwest platforms, clearing enemies as you cross the bridges.

Player character crossing a wooden bridge toward enemies below Castigator's Keep — Crossing the bridges below Castigator’s Keep toward the Alchemist’s Workshop entrance. Image: Cold Symmetry

Inside the interior, slide open the bookcase to expose the wall behind it. Strike the illusory wall to reveal the hidden path.

Sliding open a bookcase to expose the illusory wall behind it — The bookcase slides aside to reveal the illusory wall that opens the path. Image: Cold Symmetry

Clear the enemies inside, then break a second hidden wall further in. Pull the lever behind it to open the chest holding the Clockwork Shardstone.

If you prefer not to hunt for the wall, the entrance can also be exposed through the Makeshift Projectile puzzle nearby, which achieves the same result.

Desolate Keep and the Blackmarrow Key

Desolate Keep is a hidden dungeon reached from Marrow Keep. It rewards you with a Grisha Remnant from its boss and a Blackmarrow Key from the chest at the end. There are two ways in, and both start with the Slayer Seal.

Note: Take the Slayer Seal from the throne, but do not equip it. Equipping the seal disables achievements for that playthrough.

Go to the throne in Marrow Keep and take the Slayer Seal.

Head to the training room and find the podium behind the invisible wall. Break the four chains on the podium, then interact with it to teleport into the dungeon.

There is also a second, more direct entrance. Cross from Sester Genessa in Marrow Keep, reveal the illusory wall on the opposite side, and you will find the same dungeon route. A hidden chamber near Genessa holds a chalice bound by chains. Break the chains, use the Commune with Chaos interaction on the chalice, and it teleports you into the keep as well.

Explore the dungeon and defeat the Grisha boss to claim the Grisha Remnant. Work through the lifting walls until you reach the final chamber.

Open the chest at the end to receive the Blackmarrow Key. To leave, defeat the remaining enemies to open the exit, or simply reload at the beacon.

Player character fighting two armored enemies in a stone courtyard at the dungeon exit — Clearing the last enemies to open the Desolate Keep exit path. Image: Cold Symmetry

The Blackmarrow Key opens the recessed chests in Marrow Keep’s elevator room. Each chest costs one key and unlocks a color variant for a shell’s clothing, which then appears in a shade menu at any beacon. Several Blackmarrow Keys exist across the world, and the Collector sells one as well.

The Collector: the night-only vendor

The Collector is a merchant who only appears at night at the Abandoned Outpost. He sells Glimpses, Thoracium, a Blackmarrow Key, and four Tarstones, making him a priority stop for collectors. To reach him, you first need to unlock Night Mode.

Travel to Widow’s Overlook and collect the Gloombound Flame found near the beacon.

Armored character moving along a rocky path toward a wooden cart — Heading back to Marrow Keep with the Gloombound Flame to enable Night Mode. Image: Cold Symmetry

Return to Marrow Keep and take the lift to the top. Bring the flame to the extinguished lantern to light it and summon Thestus.

Speak to Thestus and choose to draw in the night. Night Mode makes enemies hit harder and increases their health, so prepare before you switch.

With night active, fast travel to the Abandoned Outpost beacon. Follow the markings toward the house and find the Collector at his night stall to buy the Blackmarrow Key, Thoracium, and his Tarstones.

Tip: You can turn Night Mode off again through Thestus, so there is no need to stay in the harder setting once you have finished your night shopping. Night Mode also opens the Shrine of Sorrows and the Forgotten Tower, which is needed for the Seedbearer’s Scripture below.

The Unfound Path secret door

The Unfound Path is the endgame area, and it hides a sealed door with a chest behind it. Access to the area itself is gated behind submitting 168 eggs in Marrow Keep. Once inside, the door opens only after three offerings are made.

Player character advancing along a path toward enemies inside the endgame area — Moving through the Unfound Path toward the three temples that unlock the sealed door. Image: Cold Symmetry

Make an offering at the Temple of Obscenity.

Make an offering at the Temple of Finality.

Make an offering at the Temple of Rebirth. With all three complete, the sealed door in the Unfound Path opens, giving you access to the chest inside.

Seedbearer’s Scripture and the final boss

The Seedbearer’s Scripture is worth the effort because it significantly weakens the final boss’s main attacks. You earn it by gathering three glands from their corrupted gates and handing them over at the Forgotten Tower, which is a Night Mode location.

Required item	Source
Faded Gland	Its respective corrupted gate
Inflamed Gland	Its respective corrupted gate
Depleted Gland	Its respective corrupted gate

Collect all three glands from their corrupted gates: the Faded Gland, the Inflamed Gland, and the Depleted Gland.

Travel to the Forgotten Tower and offer the three glands to the giant creature inside. It hands over the Seedbearer’s Scripture in return.

Keep the Scripture active for the fight against Zmey, the Unbidden. Its passive reduces the damage from the final boss’s strongest attacks, which pairs well with resistance planning for that fight’s later phases.

Common reasons a secret won’t trigger

Problem	Cause and fix
Collector is missing	You are in daytime. Light the Gloombound Flame and switch to Night Mode through Thestus first.
Achievements stopped unlocking	You equipped the Slayer Seal. Take it to open Desolate Keep, but never equip it.
Unfound Path door stays sealed	You have not completed all three temple offerings at Obscenity, Finality, and Rebirth.
Forgotten Tower gives nothing	You are missing one of the three glands, or you have not enabled Night Mode.
Merrick’s prices doubled	You killed Merrick in Marrow Keep. Buy everything you need before attacking him.

Work through these in dependency order and each reward falls into place: reveal the illusory walls for the Alchemist’s Workshop and Desolate Keep, take the Slayer Seal without equipping it, light the Gloombound Flame for the Collector, clear the three temple offerings, and finish with the glands at the Forgotten Tower for the Seedbearer’s Scripture before you face Zmey.