Ghosts of the Deep is the first of two dungeons part of the Dungeon Key in Destiny 2: Lightfall. Also, like some dungeons in the past, there are lore fragments scattered across the dungeon that provide exposition with Xivu Arath’s dialogue, called Memories of Darkness.
Collecting all 12 Memories of Darkness unlocks the “In Memoriam” triumph for the Ghoul Title. Completing this triumph also boosts the drop rate of The Navigator, the dungeon Exotic trace rifle.
This guide covers all Memories of Darkness locations in Ghosts of the Deep.
Additional links:
- Destiny 2 Ghosts of the Deep Loot Table – What Each Encounter Drops
- Destiny 2 Ghosts of the Deep Title Guide — How to Get Ghoul
- Here Are the Destiny 2 Ghosts of the Deep Secret Chest Locations
Memory of Darkness #1
The first Memory of Darkness can be found immediately after spawning into the dungeon. Look left from where you spawn and find a branch sticking out from the base of a rock formation.
Climb the rocks and walk towards the stack of sticks — which covers a hole in the rocks and brings you to an underground bunker. Follow the red door and go down the stairs to find the Memory right ahead of you.
Memory of Darkness #2
The second Memory of Darkness can be found after you clear the opening encounter and make your way to the Drilling Platform. Drop down as normal and cross the torn-up mesh wall.
Climb up the small platforms to get up to the opening. The Memory will be towards the right once you get inside the opening.
Memory of Darkness #3
The third Memory of Darkness can be found after dropping down from the tunnel like you normally would — next to the second memory you found.
Memory of Darkness #4
The fourth Memory of Darkness can be found once you clear the wave of enemies blocking your descent in the Hallowfathom area. Next, drop down the tunnel to an area with rotating platforms with ramps. Jump on the highest rotating platform in front of you and walk up the ramp. Let the platform rotate around the pillar and collect the Memory when the prompt shows up. The timing for this is more forgiving than you think.
Memory of Darkness #5
Immediately after you enter the first underwater section, turn around to see an open door with an orange light in front of it. The Memory is near the back of this small room.
Memory of Darkness #6
Once you approach the first fan in the underwater jumping puzzle, walk up the stairs with bubbles on the platform at the end of it.
Turn left from here and you will find the Memory next to an air bubble at the end of the platform.
Memory of Darkness #7
Drop down to the second underwater section but stop once you see the red light next to a crack in the wall.
Instead of jumping down like you normally would, turn left and walk around the outer rim of the tank until you see the Memory of Darkness next to a bubble.
Memory of Darkness #8
Once your objective changes to “Reach the Wreckage” underwater, turn around from where you land. You will see a yellow blowfish-esque object in a small room. Walk towards the object and collect the Memory when the prompt shows up.
The Memory can be hard to see but move your character around in the area and the prompt to collect it will show up.
Memory of Darkness #9
After you leave the underwater section where you got the last Memory of Darkness, get past the first section of ads that spawn in. Then, make your way into the next methane sea area.
When you see the giant light of the shipwreck in front of you, platform down. Then, instead of going left and fighting the next set of enemies, turn right to see an illuminated opening and head towards it. The Memory will be next to a bubble.
Memory of Darkness #10
Inside the shipwreck — once you arrive at the room with multiple holes in the wall — go to the second-to-last hole in the top row to land on the bridge. Look right to see the end of a pipe and jump there. Across this pipe is a leaking pipe with enough space for you to jump into and collect the Memory of Darkness.
Memory of Darkness #11
After defeating Ecthar, The Shield of Savathûn, leave the underwater cave. When you get to a hallway with a set of stairs at the end of it in the shipwreck, go down the stairs — you will find Cursed Thrall and a Blistered Knight here — and turn left to find the Memory behind a small cage.
Memory of Darkness #12
The final Memory of Darkness can only be unlocked after defeating Šimmumah ur-Nokru, The Lucent Necromancer. After crushing the Ghost, make your way towards the top room where you would fight the Lucent Acolyte. 
Here, you will find a ring and a symbol of Oryx. Line the symbol to the ring like you would in the boss fight to unlock a secret opening in the corner of this room. Go through the opening to find the Memory at the end of the secret room.
