Cthulhu: The Cosmic Abyss: How to Open the Portal

Cthulhu: The Cosmic Abyss is a challenging game. An entire playthrough is all about piecing clues together, solving investigations, and completing complex puzzles that may take hours.

The game doesn't hide this fact either, as it instantly puts you up against a challenging puzzle within the first 10 minutes of the game where players have to figure out how to open a mysterious puzzle. With almost no clues to start, players need to investigate the surrounding area to come up with a solution.

If you are struggling with the first puzzle in the game, this guide has you covered with everything you need to know. Here's how to open the portal in the first level of Cthulhu: The Cosmic Abyss.

How to Open the Portal in Cthulhu: The Cosmic Abyss

When you first approach the portal in Cthulhu: The Cosmic Abyss, you will notice there are two open slots where items can be placed into. It's your job to find the correct items in the house and place them in the slots in order to open it.

To figure out which items the portal requires, you need to solve the paper mural puzzle on the first floor. If you look below the mural, you will find pieces of paper on the ground that you can pick up.

Pick up the pieces of paper and rotate them to align with the lines of the mural on the wall to reveal the two items you need for the portal in the basement. Your mural should resemble the image below.

The two items that you need to find are revealed to be mineral pieces. More specifically, you need to find Fused Quartz and Basalt Rock, which can be found by investigating different locations throughout the house. The next two sections explain how to find them.

Fused Quartz Location

First, let's start off with finding the Fused Quartz. The Fused Quartz mineral can be found on a shelf on the right-hand side of the main office on the first floor of the house. The image below shows you the exact location of the Fused Quartz.

Once you have it in hand, select the option to pick it up and make your way down to the basement. Remember, according to the paper mural we pieced together earlier, the Fused Quartz goes in the right slot. Place it down in the slot on the right-hand side.

Basalt Rock Location

Next, you need to find the Basalt Rock to officially open the portal in Cthulhu: The Cosmic Abyss. The Basalt Rock mineral can be found behind the bed, as shown in the image below.

Once you pick up the Basalt Rock mineral, your character will talk about how it pulsates a strange energy. This is giving you a hint that you are currently in possession of the correct item to open the portal.

Bring the Basalt Rock into the basement and place it in the slot on the left-hand side of the portal which the paper mural showed us earlier in this puzzle. Doing so will activate a cutscene, where you are forcefully sucked into the portal and brought to a different dimension.