Cthulhu: The Cosmic Abyss – 100% Achievement Guide

Overview

Welcome to the Spire of Completion’s 100% achievement guide for Cthulhu: The Cosmic Abyss, a Lovecraftian investigation thriller featuring 27 achievements / 28 trophies.

Roadmap

Step 1/1 (8 hours)

• Don’t enable Free Clue Analysis in the difficulty settings.
• Reconstruct Mei’s drawing in Chapter 1 (see Artist).
• Solve all 4 Investigations with the Decrease options (see Mens Sana).
• Find all collectibles (Energy Upgrades, Sub-Clues, Deductions, Evolutions, Analyzable Clues).
• Don’t exceed the Corruption threshold and prevent Cthulhu from awakening (see A New Watcher).

Story Achievements

Spoilers

The Awakening

Find Mei in the Other World.

Let there be Light

Reactivate the PIT station.

The Excavation

Cross the maze.

The Temple

Escape from the deep one.

The Other World

Leave the Other World.

The Citadel

Get the Star of Shamash.

The Last Door

Reach the prison.

Cosmic Abyss

Replace the watcher.

Endings

The game features two endings:

• Good Ending: Prevent Cthulhu from awakening.
• Bad Ending: Awaken Cthulhu.

For the Good Ending, be sure to keep your Corruption below the threshold (see Mens Sana) and stab the Star of Shamash or throw the Device to Elsa, who is kneeling on the left in the final scene.

For the Bad Ending, throw the Device to Key, who is standing on the right in the final scene.

Both endings can be unlocked in a single playthrough by loading the last autosave after the credits, but only the Good Ending rewards an achievement.

Missable Achievements

Throughout the game, your Corruption level will inevitably increase. To keep it below the threshold (trackable in the Control menu), be sure to:

• Reduce the Corruption Rate in the difficulty settings (can be set to 0).
• Use Energy to analyze clues, not Corruption. You can recharge Energy with Stimulants.

Additionally, there are 4 Investigations in the game, each offering exactly two solutions that either slow down (decrease) or accelerate (increase) the spread of your Corruption. Be sure to choose the Decrease solutions in all Investigations:

Chapter 2: Get Through the Maze

• Decrease: Follow the traces through the current (see Against the Tide).
• Increase: Reassemble the Artifact and place it on the Stone Pedestal.

Chapter 3: Go to the Portal

• Decrease: Power up the Energy Network (see In Deep Waters).
• Increase: Complete the Crown Ritual.

Chapter 5: Neutralize the Guardian

• Decrease: Hypnotize the Guardian (see His Master’s Voice).
• Increase: Kill the Guardian.

Chapter 6: Open the Last Door

• Decrease: Activate all 5 Metal Plates in the Antechamber (see Better than Pandora).
• Increase: Activate fewer than 5 Metal Plates in the Antechamber.

In Chapter 1, reconstruct Mei’s drawing in the Dining Room:

All 5 missing Pages can be found around the table in the Dining Room (one is on the back of the Receipt).

In Chapter 2, exit the Maze without placing the Repaired Artifact into the Stone Pedestal. Instead, obtain the Hybrid Mucus Frequency from the Transfer Module and follow the traces through the Maze and the current. To access the flooded Transfer Module:

1. Interact with the Drainage System in the Control Module to start a deduction.
2. Solve the deduction with the clue Strange Matter (scattered across the Station).
3. Analyze the Titanium Pipe to the left of the Drainage System to get the Titanium Frequency.
4. Combine the Titanium and Extra-Dimensional Sap Frequencies to identify a clogged Titanium Pipe.
5. Find a new Titanium Pipe in the nearby Storage Module and replace the clogged pipe.
6. Interact with the Control Panel of the Drainage System to drain the Transfer Module.
7. Find the Hybrid Mucus Sample in the drained Transfer Module.

In Chapter 3, locate Anastasia Wolejko’s Laptop by the Sacrificial Altar and use the External Battery from the Ocean-I tent in the Tombs to power it up, then read the entry about the translation database:

In Chapter 3, reach the Temple without performing the Crown Ritual. Instead, power up the Energy Network to destroy the Deep One blocking the Temple Exit:

1. Climb the scaffolding in the Nave and jump down on the Brittle Stone to break into the Reservoir.
2. Analyze the Cylinder to get the Unknown Alloy and Electrum Frequencies.
3. Repair the Metal Apparatus with the Cylinder, then head back to the Choir.
4. Pass through the Wing of Secrets to the Secret Sanctuary (Bas Reliefs: go forward, otherwise go back).
5. Use the Unknown Alloy Frequency to locate the Metal Cube in the Secret Sanctuary.
6. Transform the Metal Cube to a Sphere with the Electrum Frequency, then place it in the Metal Plate.
7. Dive through the Submerged Antechamber toward the Pedestal Chamber.
8. Power up the submerged Metal Plate with the nearby Metal Cube (use the Unknown Alloy Frequency).
9. Find the Metal Cube in the Ocean-I Lab and power up the final Metal Plate in the Choir.

In Chapter 5, examine the Incomplete Prayer Stele in the Atrium to start a deduction:

Reach the Laboratory across the chasm to find the other part of the Incomplete Prayer Stele and use it to solve the deduction:

In Chapter 5, combine these Sonar Frequencies to reveal the Invisible Tentacles of the Guardian:

• Human Blood
• Macroplankton
• Shoggoth Heart

Analyze any dead body in the Atrium for the Human Blood Frequency. The Macroplankton and Shoggoth Heart Frequencies can be found in the Laboratory across the chasm.

In Chapter 5, don’t kill the Guardian. Instead, hypnotize it:

1. Find the first Metal Quoit in the Ocean-I camp at the entrance to the Atrium.
2. Access the House of Words and find the second Metal Quoit on the second floor.
3. Use both Metal Quoits to enter the Forge in the House of Words.
4. Place Zirconium in the Complex Mechanism, then activate it with a Metal Quoit.
5. Take the Yith Orb: Zirconium and place it in the metal slab halfway up the Tower of Shamash.

In Chapter 6, analyze the pillar Prayer of the Masters in the Antechamber to get the Gold Symbols and Ultrasonic Stone Frequencies. Combine both Frequencies, then head down the stairs on the left and open the Engraved Door at the bottom with the Sonar Waves:

In Chapter 6, open the Engraved Door, then engrave the Star of Shamash with the Symbol of Kelendhar. Place the Star of Shamash on any Base in any Mausoleum with the symbol facing toward you. Look at the symbol for a few seconds to activate the Star of Shamash, then pick it up to teleport to the Secret Lodge:

Miscellaneous Achievements

Reveal 25 clues using Sonar Frequencies. Sonar Frequencies are an integral component of the game and are used to reveal clues from afar. You will most likely reveal 100+ clues during your playthrough. Hold RMB to increase the range of the Sonar Waves.

Use 10 Stimulants to recharge your Energy. Be sure to leave Free Clue Analysis disabled in the difficulty settings. Otherwise, you will barely consume Energy and won’t be able to use enough Stimulants.

Interact with Young or Mature Lichen to turn them into Stimulants. They can be found throughout the game and glow orange:

Collectibles

There are 5 different types of collectibles scattered across the game:

• Energy Upgrades (all 4 required).
• Sub-Clues (only 10 required).
• Deductions (only 15 required).
• Evolutions (all 17 required).
• Analyzable Clues (only 25 required).

Below, the exact number required to unlock each achievement is covered, but more Sub-Clues, Deductions, and Analyzable Clues can be found. Progress for all collectibles is counted across all save files.

Chapter 1 – The Awakening

Sub-Clue 1/10: Engraving of a City

Behind Elsa in the Library:

Analyzable Clue 1/25: Green Elbaite (Mineral)

On the coffee table in the Library:

Sub-Clue 2/10: Ancient Flask

On the small shelf in the Library:

Sub-Clue 3/10: Basalt Rock

Behind the mattress in the Dining Room:

Sub-Clue 4/10: Receipt

On the table in the Dining Room:

Sub-Clues 5-9/10: Fused Quartz, Ancient Tablet, Triangular Prism, Clay Vase & Onyx Statuette

In the cabinet in the Office:

Sub-Clue 10/10: Incident Report: PIT Station

On the desk in the Office:

Chapter 2 – The Excavation

Deduction 1/15: Why did the stone become activated?

Unmissable tutorial deduction.

Solution

Correct Clue: Incident Report: PIT Station

Analyzable Clue 2/25: Fungal Species (Lichen Stimulant)

Unmissable story-related analysis in the Control Module of the Station:

Analyzable Clue 3/25: Strange Matter (Extra-Dimensional Sap)

Spread around the Station:

Analyzable Clue 4/25: Compromised Hydrogen Canister (Hydrogen)

In the Machine Module, to the left of the Reactor Control Panel:

Analyzable Clue 5/25: Service Memo (Electronic Component)

Scattered around the Station, the first can be found in the Machine Module under the stairs:

Analyzable Clue 6/25: Anchor (Copper)

By the South Exit leading to the Maze:

Analyzable Clue 7/25: Stone Pedestal (Astral Stone & Extra-Dimensional Sap)

At the Maze Entrance:

Analyzable Clue 8/25: Ancient Structure

Surrounding the Stone Pedestal at the Maze Entrance:

Evolutions 1-3/17: Stimulating Discovery, Amplified Sonar & Recycling
Analyzable Clue 9/25: Strange Tablet (Elders Glyph)

In a separated room at the Maze Entrance, near the Stone Pedestal:

Analyzable Clue 10/25: Scratches (Alpha-Keratin)

In front of the Strange Tablet at the Maze Entrance:

Analyzable Clue 11/25: Body of Arif El Fassi (Human Blood & Alpha-Keratin)

Follow the red Lifeline and the Anchors through the Maze:

Analyzable Clue 12/25: Photograph: Current (Documents)

In the Ocean-I Camp at the end of the red Lifeline in the Maze:

Deduction 2/15: How did Marsh’s crew manage to make its way through the labyrinth?

Automatically started upon swimming through a wrong tunnel in the Maze.

Solution

Correct Clue: Stone Pedestal

At the Maze Entrance:

Deduction 3/15: Where did the unidentified entity revealed by the station logs go?

Back in the Station, read the PIT Station Logs in the Control Module to start the deduction:

Solution

Correct Clue: Motion Capture Camera: Image 3

Examine the console next to the PIT Station Logs:

Deduction 4/15: Why can’t the transfer module be drained?

Interact with the Drainage System in the Control Module to start the deduction:

Solution

Correct Clue: Strange Matter

Scattered across the Station:

Analyzable Clues 13-14/25: Titanium Pipe (Titanium) & Steel Pipe (Steel)

Next to the Drainage System in the Control Module:

Analyzable Clue 15/25: Hybrid Mucus Sample (Hybrid Mucus)

In a crate in the Transfer Module (see Against the Tide for how to access the Transfer Module):

Evolution 4/17: Occult Overload

In another crate in the Transfer Module (see Against the Tide for how to access the Transfer Module):

Analyzable Clue 16/25: Body of Terell Curtis (Human Blood)

In the Medical Module on the first floor:

Deduction 5/15: What are the supposed effects of the artifact on the crew?

Read the Notes from Jeremy Bernard in the Medical Module to trigger the deduction:

Solution

Correct Clue: Terell Curtis’ Medical File

Examine the laptop next to the Notes from Jeremy Bernard:

Analyzable Clue 17/25: Camille Aubert’s Key Card (Key Card)

In the Science Module on the second floor:

Deduction 6/15: Where is the last fragment of the artifact to be found?

Open the Decontamination Chamber in the Science Module with Anastasia Wolejko’s Key Card (to find it, equip the Key Card Frequency and jump across the crates in the Quarters), then combine the two Artifact Fragments to start the deduction:

Solution

Correct Clue: Recording: Anastasia Wolejko

In the Communication Module on the first floor, by the North Exit:

Chapter 3 – The Temple

Analyzable Clue 18/25: Stele (Basalt)

In the Nave shortly before Camp Mu:

Analyzable Clue 19/25: Sacrificial Altar (Human Blood, Extra-Dimensional Sap & Ancient Blood)

Examine the Sacrificial Altar in the Choir.

Analyzable Clue 20/25: Ancient Crown (Ancient Blood & Orichalcum)

Behind the Sacrificial Altar:

Analyzable Clue 21/25: Battery (Electronic Component & Lithium)

To the right of the Sacrificial Altar:

Deduction 7/15: How did the Ocean-I translate the engravings in the temple?

Examine the Engraved Tablet to the right of the Sacrificial Altar to start the deduction:

Solution

Correct Clue: Computer Belonging to Anastasia Wolejko

Locate the External Battery in the Ocean-I tent in the Tombs and use it to power up Anastasia Wolejko’s Laptop next to the Engraved Tablet in the Choir:

Deduction 8/15: What does the statue represent?

Examine the Statue with Three Eyes to the right of the Sacrificial Altar to start the deduction:

Solution

Correct Clue: Stele: Hydra

After solving Deduction 7, examine this Stele in the Nave:

Deduction 9/15: What does the statue represent?

Examine the Statue with Fangs to the left of the Sacrificial Altar to start the deduction:

Solution

Correct Clue: Stele: Dagon

After solving Deduction 7, examine this Stele in the Nave (pass through Camp Mu):

Evolution 5/17: Dynamic Sonar

Enter the Ocean-I Lab and head down the rocks by the left bridge, then follow the stream:

Analyzable Clue 22/25: Metal Cube (Unknown Alloy)

On the desk in the Ocean-I Lab:

Deduction 10/15: What was the purpose of the metal base Ocean-I damaged?

Read the Note: Metal Sphere Extraction in the Ocean-I Lab to start the deduction:

Solution

Correct Clue: Metal Plate

Examine the Metal Plate between the Choir and the Tombs:

Analyzable Clue 23/25: Brittle Rock (Invasive Algae)

Near the scaffolding in the Ocean-I Lab:

Analyzable Clue 24/25: Cylinder (Unknown Alloy & Electrum)

Climb the scaffolding in the Nave and jump down on the Brittle Stone to break into the Reservoir:

Analyzable Clue 25/25: Metal Slab (Unknown Alloy)

In the Reservoir under the Nave:

Energy Upgrade 1/4

Follow the left path out of the Reservoir:

Deduction 11/15: How do you cross the Hall of Secrets?

Listen to the Conversation between Selina and Calla in the Antechamber to start the deduction:

Solution

Correct Clue: Funeral Stele

After solving Deduction 7, examine this Funeral Stele in the Tombs:

Evolution 6/17: Occult Sonar

Hidden under a Stele in the Tombs:

Evolution 7/17: Mental Synthesis

Equip the Elders Glyph Frequency (analyze any Strange Tablet to obtain it), then enter the Submerged Antechamber and dive through the Submerged Wing. Use the Sonar to locate the sunken Strange Tablet:

Chapter 4 – The Other World

Evolution 8/17: Occult Evolution

Open the door in the Hall of the Abyss (before jumping into the well). To open it, analyze the Inset next to the door to get the Astral Stone Frequency. Use this frequency to find the Stone Seal in the Ossuary:

Evolution 9/17: Occult Barrier

In the Ocean-I Camp, after diving through the water to find another passage (enter the cave straight ahead):

Energy Upgrade 2/4

In the Ocean-I Camp, after diving through the water to find another passage (follow the path on the left):

Evolution 10/17: Occult Recharge

In the Submerged Ruins, immediately after blocking the waterfall:

Evolution 11/17: Occult Healing

In the Gallery of the Fall, crawl through the hole on the right:

Chapter 5 – The Citadel

Deduction 12/15: How to translate these strange alphabetic symbols?

Examine the Incomplete Prayer Stele in the Atrium to start the deduction:

Solution

Correct Clue: Incomplete Stele

Examine the Incomplete Stele in the Laboratory across the chasm:

Deductions 13-15/15: What creature was used as an envelope for the Guardian?

Examine the Stele: The Guardian’s Growth in the Laboratory on the second floor to start the deduction:

Solutions

Correct Clue #1: Shoggoth Heart

In the Laboratory on the first floor:

---

Correct Clue #2: Stele: Unexpected Result

In the Laboratory on the second floor:

---

Correct Clue #3: Macroplankton Sample

In the Laboratory on the first floor:

Evolution 12/17: Efficient Synthesis

Unlock the Invisible Tentacles Frequency, then reach the Elder’s Tablet in the Atrium:

Evolution 13/17: Improved Syringe

First, find the Metal Quoit in the Ocean-I camp at the entrance to the Atrium:

Then, place the Metal Quoit on the Metal Box in the Laboratory (second floor) to open it:

Evolution 14/17: Mental Barrier

Use the Metal Quoit to enter the House of Words and open the Metal Box on the second floor:

Energy Upgrade 3/4

Halfway up the Tower of Shamash, follow the Invisible Tentacles to the Energy Upgrade:

Evolution 15/17: Stimulating Thought

Halfway up the Tower of Shamash, follow the Invisible Tentacles, then jump down to the Strange Tablet:

Chapter 6 – The Last Door

Evolution 16/17: Mental Healing

Open the Engraved Door, then engrave the Star of Shamash with the Symbol of Kelendhar. Next, locate the Memorial of Possibilities and place the Star of Shamash in the Pillar of the Jailers to start a Reconstruction:

Energy Upgrade 4/4

Use the Star of Shamash to teleport from the Secret Lodge to the Mausoleum of the Engineer:

Evolution 17/17: Occult Release

In the Antechamber, accessible after experiencing all 3 Reconstructions in the Mausoleums:

If you enjoy Lovecraftian games, check out my Call of the Sea – 100% Achievement Guide!

Many thanks to Nacon for providing me with a free copy of this game.