Cthulhu: The Cosmic Abyss Chapter 3 Ritual Puzzle Guide

Developed by Big Bad Wolf, Cthulhu: The Cosmic Abyss is an investigative title that leans heavily into complex puzzles from the very first second. So if you find yourself stuck in the early game, don’t feel bad, since it is entirely intentional!

The developers designed these challenges to make players truly rack their brains. While the first two chapters already demand a Sherlock Holmes level of intuition, Chapter 3: The Temple is the first one that proves that the focus on atmospheric tension and puzzle-solving is real here.

That’s because this chapter drops you right into the middle of an ongoing ritual in R’lyeh, the sunken city, and requires you to finish it yourself. To succeed, you must overcome a series of complicated riddles in a specific order and even learn to translate the R’lyehian language.

But don’t worry – this guide will help you navigate the mysteries of the third chapter and describe every necessary step in the most straightforward way possible.

How to Get the Battery & Turn on the Computer

As soon as the chapter begins, you will have three paths to choose from: left, right, and straight ahead to a small area. Your first priority must be finding a way to access the computer located on the right side of the altar (the one with the man fused to it), which is sitting on top of a crate.

Interact with the device to discover that it belonged to Anastasia Wolejko, one of the main scientists of Ocean-I, and that it contains her research on the R’lyehian language. Since almost every important inscription here is written in that tongue, and you’ll need to understand to progress, translating it is your first major task here.

However, the computer is dead, which means you need to find an external battery to power it up. You’ll notice a battery is already plugged in, but it’s covered in a strange substance. Upon analysis, you’ll discover it has suffered from corrosion and is filled with Helium and Potassium Hydroxide. These two elements will then be automatically added to your Sonar, and the latter will be very important soon.

Now, follow the path behind the altar to find a small Ocean-I camp with some crates inside. Open the one on the left to find more batteries, but analyzing them reveals they are filled with Lithium instead of Helium, meaning something strange is happening to the equipment here.

Right in front of the camp, there are two tables. Interact with the one on the far left (in front of a tomb) to find a document explaining that the batteries corrode and become useless whenever they are near a specific metal.

With this information, you can deduce that you need a functional battery containing only Lithium and Potassium Hydroxide, so activate these two elements in your Sonar and scan the camp area to find a working battery! Take it back to the computer to unlock Anastasia’s research, finally allowing you to read the mysterious temple inscriptions.

Finishing the Ritual: The Three Ancient Crowns

Once you can translate the text, it’s time to complete the ritual that the Ocean-I members started before losing their minds. The ritual consists of three steps: finding three ancient crowns, blessing them, and placing them on skeletons seated on thrones.

Fortunately, two of the three crowns are quite easy to find, since they are “hidden” in the starting area. The first is right behind the main altar on the floor, and the second is on the table in that camp where we found the battery. The last one is hidden in the left passage, so we’ll get that later.

Before proceeding to the right path, notice that on the back of the stone holding the man in pain, there is a small pool of blood you can interact with. This is where you must bless the crowns by dipping them into the blood! So take the two crowns you’ve just found and bathe them in this blood before moving forward.

How to Get Past the Hall of Secrets

When you take the path to the right of the altar, you will find yourself in the Hall of Secrets. This is basically a maze where you must choose the correct path to advance, but there are only two options: move forward or turn around.

An audio log in the area reveals a conversation between Ocean-I members, mentioning that Anastasia actually discovered how to beat this maze by studying the tombs near the camp, which contain some text in an ancient language.

Since you already have the R’lyehian translation, return to that same camp from before and interact with the tombs (only two of them, since the third one is broken). By doing that, you'll discover that the secret to overcoming the Hall of Secrets lies in the bas-reliefs on the walls.

Just make sure to interact with every bas-relief as they explain the lore behind the ritual we are performing! If you’ve done everything correctly, you’ll reach the end of the hall, where a skeleton on a throne awaits. Examine the Ancient Crown with the Eye (flip it in your inventory to confirm it has the eye symbol), and place it on your dead pal to complete the first step.

How to Get Past the Pool of Blood

Return to the altar. Before taking the left path, ensure you have analyzed both your remaining Ancient Crown and the altar blood, as this registers Ancient Blood and Orichalcum in your Sonar. So activate them and head down to the left passage from the main area.

You’ll find yourself in a place flooded with blood and a body that seems to have been sacrificed right in the center. Near this sacrificial corpse, you’ll see two scary sculptures on both sides of the wall. So head toward the one on the right, where the water is deep enough to swim, and dive to find a secret passage. Your Sonar is your best friend here, since that combination of Ancient Blood and Orichalcum will point toward the last missing Ancient Crown and also allows you to see through the murky, blood-filled water.

In the first underwater area, you can surface to find some corpses to analyze and a small structure you can climb. Follow it to the end and jump onto the floor in front of the open tombs to reveal another secret passage. Swim through using the Sonar to find the final Ancient Crown, which has a claw symbol on it (don’t forget to analyze it!).

Now, exit this area and return to the blood pool, looking for some underwater stairs to follow that lead to a second skeleton on a throne. This skeleton requires the ancient crown you just picked up, but you need to bless it first, remember? So head to the exit (right in front of the throne) to find a locked door that requires a round object to open – luckily for us, it is on the floor where you are standing right now, near a corpse and an audio log.

Grab it and open the door to find yourself back in that first area with blood (with the sacrificial corpse). Simply return to the altar to bless the final crown with blood and place it on the skeleton to complete the second major step.

How to Start the Ritual

By placing the second ancient crown on the skeleton, green slime will appear throughout the temple, especially in the main area with the altar. Head back there to discover another skeleton sitting on a throne right in the middle of the room, along with some uncomfortable proof that the ritual is working, as the man trapped on the altar will be in an even worse state than before.

Now, all you need to do is place the remaining Ancient Crown, which is the one with the Tentacles, on the skeleton that just appeared. Doing this will finally start the ritual, completing Chapter 3 and opening the path to the portal. Oh, and you’ll also meet a Deep One, one of the creatures that will appear frequently from this point forward.