Mortal Shell 2: Blackwell Cavern Walkthrough and Triarch Repeater Location

Blackwell Cavern is one of the smaller dungeons in Mortal Shell 2, and it is worth the detour for a single reason: the Triarch Repeater, a minigun-style sidearm sitting on the cavern floor. The dungeon itself is short, dark, and packed with Wraiths, but the path to it is the part that trips people up.

Quick answer: From the Castigator’s Keep Beacon, drop down behind the beacon, take the elevator to the valley, and follow the cliffside path north until you reach a torchlit cave entrance. Head inside, ride the second elevator down, and loot the body beside the lit Wraith to receive the Triarch Repeater.

Blackwell Cavern location: below the Castigator’s Keep Beacon

The cavern sits in the Ruins of Mammon, on the lower cliffs underneath Castigator’s Keep. If you are coming from the Outskirts of Mammon, the overland route runs through the Road to Absolution and into Castigator’s Keep itself, where the keep’s elevator drops you to the valley paths that lead to the cave mouth.

Detail	Blackwell Cavern
Region	Ruins of Mammon
Nearest beacon	Castigator’s Keep
Entrance	Torchlit cliffside cave, north of the beacon
Reward	Triarch Repeater (sidearm) x1
Enemies	Wraiths, Mycellian Skulks
Missable?	No, it can be cleared any time in free roam

Note: dungeons only appear on your map once you pass through the fog gate for the first time, and the game does not tick them off automatically. You mark them yourself by hovering the cursor over the icon on the map.

Route to the cave entrance from Castigator’s Keep

Fast travel to the Castigator’s Keep Beacon and open the map to confirm your position. The cavern lies below and north of you, so everything from here is a descent.

Climb the stone stairs through the upper ruins of the keep. There is a pedestal along this stretch holding a Synaptic Vessel, so grab it before you move on.

Player climbing stone stairs in Castigator's Keep as a Weltcap pickup notification appears — Climbing the stone stairs through the upper ruins of Castigator’s Keep. Image: Cold Symmetry

Cross the wooden scaffolding at the back of the keep and drop down a level. Hit the switch at the elevator platform and ride it down to the green valley below.

Player riding the wooden elevator down from Castigator's Keep in a green glow — The elevator behind the keep drops you to the valley paths. Image: Cold Symmetry

Follow the narrow cliff paths and grassy ledges north. Winged creatures swoop in along the way and are easiest to knock down with a sidearm before they close distance.

Push through the enemy camps on the foggy hillside, where cloaked humanoids sit around tents and campfires. Keep hugging the cliff edge past them and the torchlit cave opening comes into view at the end of the path.

Inside Blackwell Cavern: the descent and the Wraith ambush

Walk through the fog door into the mine tunnel. The Blackwell Cavern banner appears here, which also registers the dungeon on your map.

Follow the torchlit tunnel to a second elevator and ride it deeper underground. At the bottom, squeeze through the gap in the wooden beams to enter the dungeon proper.

Armored player character with sword drawn on the wooden elevator platform inside the mine — The second elevator, inside the cave, takes you down to the cavern’s main chamber. Image: Cold Symmetry

Step into the main area and expect your vision range to drop sharply. A group of Wraiths ambushes you the moment the darkness closes in, so fight with your back to a wall rather than chasing them into the black.

Player moving through the dark cavern tunnels as a Laterite pickup notification appears — Working through the dark cavern tunnels toward the lit chamber. Image: Cold Symmetry

How to get the Triarch Repeater

Look for the one Wraith standing near a light source in the chamber past the ruined cart and debris. The dungeon’s reward is lying on the ground right beside it, next to a body, and interacting with it triggers the New Weapon Acquired prompt for the Triarch Repeater.

There is a readable letter in the same spot, which is flavor rather than a requirement:

What is honor but another chain around the fool’s neck. If you have courage, seize the war-engine and turn it upon these louts. Prove yourself their better and a reward awaits

To confirm the pickup landed, open your character menu and check the Sidearms tab. The Triarch Repeater should be listed there and equippable immediately.

Sidearms inventory screen showing the newly acquired Triarch Repeater — The Triarch Repeater listed in the Sidearms tab after pickup. Image: Cold Symmetry

Clearing the Mycellian Skulks and leaving the dungeon

A horde of Mycellian Skulks rushes you in the passage beyond the pickup. This is the ideal place to equip the Triarch Repeater and test its burst fire, since the group is tightly packed and the weapon shreds through them faster than melee does.

Once they are down, there is nothing else to collect. Backtrack through the corridors to the elevator, ride it up, and step out through the fog gate onto the cliffside.

Tip: because completion tracking is manual, open the map after you leave, move the cursor onto the Blackwell Cavern icon, and toggle it so the dungeon no longer reads as incomplete.

If the dungeon icon never appeared on your map, you did not cross the fog gate at the cave mouth, and if the Triarch Repeater is missing from your Sidearms list, you likely cleared the Wraiths without looting the body beside the lit one. Nothing here is missable, so you can return to Castigator’s Keep and run the short loop again at any point.