How Get to the Star of Shamash in Cthulhu: The Cosmic Abyss

The further you descend into the depths of Cthulhu: The Cosmic Abyss, the more you realize that the Big Bad Wolf team has a cruel talent for making players feel unwelcome with more Lovecraftian horrors.

While earlier chapters were a test of your mental acuity, Chapter 5: The Citadel shifts the focus toward your survival instincts, plunging you into an environment that is as much a living organism as it is an ancient ruin.

That’s because this is where the game introduces its most repulsive obstacle yet: a gargantuan, pulsating mass of sentient slime that has claimed the hallways of the Citadel as its own – and that reacts to your every step! Stay on its surface for a second too long, and it will claim the protagonist Noah as its next meal.

This entity stands directly between you and your next main goal: the Star of Shamash. The artifact is perched at the very top of the creature’s lair, meaning you’ll need to cautiously explore every inch of this repulsive environment to find a way to reach it successfully.

If the sight of the Citadel’s living floors has you feeling stuck, don't worry! This guide breaks down the safest route through the filth, ensuring you reach the Star without becoming a meal for this grotesque creature.

How to Avoid the Guardian & Learn the Gold Symbols

As soon as you gain control at the start of the chapter, you’ll notice various slimes scattered across the area. Approach one and examine it to discover it is a Milky Matter composed of Organic Secretion, which will be automatically added to your Sonar.

These slimes are part of the massive, multi-eyed monster at the center of the zone, which is known as The Guardian. Stepping on them alerts the creature to your position, leading to an immediate “Game Over” if you linger too long. Fortunately, by activating the Organic Secretion element in your Sonar, you can highlight these hazards and avoid them! So do that now.

Before moving forward, look right behind you (behind some non-interactive objects) for an item that soon will be important: the Metal Quoit. Grab it now and leave it in your inventory. Then, carefully navigate through the only available path, avoiding the slime (you need to jump the first one, by the way) until you reach a chasm too wide to jump.

Before trying to cross, check your surroundings for an audio log and an Incomplete Prayer Stele. Examining both will reveal a text written in Gold Symbols that needs translation – this will open a new deduction in your Vault and also add the gold symbols to your Sonar. You’ll also learn that the slime isn't just a trap, but it can be used as an invisible platform to advance! So use your Sonar to reveal the floating milky matter over the chasm and jump toward it to reach the other side.

Follow the path into an enclosed laboratory where you’ll discover that Deep Ones and other bizarre creatures were artificially created. There is plenty to examine across two floors, so here are the most important ones:

• Macroplankton: Located in a broken tank on the floor near the right side of the entrance, surrounded by dead larvae.
• Human Blood: Follow the trail of blood to the left of one of the biggest tanks in the room (the one that contains a dead Deep One) to find a blood stain on the floor.
• Shoggoth Heart: Found in the very last broken tank on the right-hand wall.

Before heading to the second floor, there is one more thing to analyze: a broken stele right behind the three biggest tanks of the room. Simply go around them on the right side, then crouch down to crawl under the cable and reach another stele, the Incomplete Prayer Stele, which allows you to complete that deduction from before in your Vault! So do that to discover that the key to reading the Gold Symbols lies on the other side of the chasm on the second floor, which is currently blocked by invisible walls.

Now, finally, proceed to the second floor to get the full picture of the situation. Basically, to cross, you must combine the three elements that compose the Guardian in your Sonar.

Luckily for us, you already did that! Simply combine Human Blood, Shoggoth Heart, and Macroplankton. By using the Sonar with this combination, it will reveal the Guardian’s invisible tentacles on the second floor, which you can use as a bridge.

On the other side, interact with the complete stele to finally translate the Gold Symbols. Then, use your Metal Quoit in the small box nearby to find a tablet with instructions on how to distract the Guardian by forging a Mysterious Orb, which will be valuable information soon! Also, don’t forget to grab the Metal Quoit and put it in your inventory again.

How to Forge the Orb

From the area you just discovered how to translate the gold symbols, look for an opening that leads outside, and use the Guardian’s tentacles as a bridge. By doing this, you’ll be at the main structure of the area, which is also the lair of the enormous creature – and has the Star of Shamash (our current main objective) at the top.

Now, you must find a way to neutralize the Guardian to reach the glowing object. Your first step is to return to the chapter's starting area (near the first giant eye) and head through the debris on the right, which is now accessible. Immediately after passing the first tentacle, look for a cramped passage on your right that requires you to crouch. Follow it to the end and use a Metal Quoit to open the door.

Explore the first floor, then head upstairs. You’ll find two doors: one that opens with your Metal Quoit and one that is locked. Enter the accessible room and analyze everything, specifically the stele that provides the “Tablet: Register of Matter” clue for your Vault.

Before leaving this room, pick up the second Metal Quoit that lies on the floor, which will open that previously locked door! Simply place one Quoit on the floor right in front of the door and hold the second one to open it.

Inside this forge room, open the chest on the far right with a Quoit and analyze the tablet to trigger a new deduction. The answer to this puzzle is the "Tablet: Register of Matter" you just found in the previous room, and solving it reveals that the distraction orb must be crafted from Zirconium!

Locate the Zirconium among the metal shelves (you don’t need to waste energy to analyze them all, just the Zirconium), then take it to the wall mechanism acting as a forge, and replace the incorrect metal already inside with yours. Now, all you have to do is use a Metal Quoit on the forge's side panel to craft the Yith Orb made of Zirconium. This will be your “weapon” against the Guardian!

How to Neutralize the Guardian

With the yith orb in hand, head through the back exit of the previous room. You’ll find yourself in an area filled with slime. Trigger your Sonar (with Human Blood, Shoggoth Heart, and Macroplankton combined) to reveal a tentacle path leading back to the main structure, where the Guardian is.

Now, climb the stairs until you find a metal plate on the floor designed to hold a sphere (you need to drop on the platform to reach it). Then, place the Yith Orb made of Zirconium on the plate to trigger a cutscene, which will end with successfully distracting the Guardian!

With the creature occupied, you can finally climb its massive tentacles to reach the Star of Shamash, without getting killed, and complete the fifth chapter of Cthulhu: The Cosmic Abyss. Oh, and reaching the top also reveals the tragic fate of the scientist Marsh, a pivotal moment for the game’s narrative.