Treacherous Light of the Depths is a World Quest introduced in Fontaine in Genshin Impact 4.1. See how to unlock this quest, its walkthrough, and all the rewards of this quest here in this guide!

How to Unlock Treacherous Light of the Depths

Quest Unlock Requirements

Quest Unlock Requirements
	Aha! Looks like Treacherous Light of the Depths is not locked behind any quest!

Go to the Fontaine Research Institute Region

Treacherous Light of the Depths is located in the Fontaine Research Institute Region, in the nation of Fontaine. Use the Teleport Waypoint and dive into the water to discover a blocked-off cavern entrance.

Clear the Rock Using the Jellyfish's Ability

You will see a rock and a Xenochromatic Jellyfish near it. Use the Xenochromatic Jellyfish's Ability to clear the rocks. Once the entrance is open, proceed deeper into the cavern.

Swim and Explore

Continue swimming down until you land on a puddle. Head down the path until you see a metal door with a switch nearby. Interact with the switch and the door will open to another area, where the Treacherous Light of the Depths World Quest starts!

How to Get to Fontaine and Map Guide

Treacherous Lights of the Depths Walkthrough

Explore Inside the Ruins

Once you enter the ruins, a short dialogue plays between you and Paimon. Since there is a light-emitting device, follow the beam of light to reach the first optical device that you need to interact with.

Find the First Optical Device

The first optical device is located on the upper right side of the ruins. Glide down towards the middle area then make your way through the broken bridge to get to it.

Start the First Optical Device

Now you need to start the first optical device. Activate it and wait until the image becomes clear before calibrating it! It will emit a beam of light if you are successful in starting it.

Find the Second Optical Device

Follow the beam of light that the first optical device emitted to find the second optical device. It is located in the lower area of the ruins. Take out the Clockwork Meka that are guarding it first.

Start the Second Optical Device

Starting the second optical device is not so easy this time. It is missing a component, which is locked in a room behind a metal door. Interact with the Energy Transfer Terminal nearby to start unlocking the door.

Use the Viewfinder to Unlock the Metal Door

Once in the viewfinder, find the next viewfinder to get a better angle. You will then see two energy cells, so transfer the energy of the right cell to the left cell. This should unlock the metal door and allow you to collect the component.

Take the Component

Exit the terminal and enter the room. Take out the Clockwork Meka then take the component buried in the sand where the Meka was facing. Bring it back to the second optical device so you can start it.

Calibrate the Second Optical Device

You can now activate and calibrate the second optical device. This time, there will be two images so you need to calibrate it twice. Remember to wait for the image to become clear before calibrating it.

Freeing the Seelie in the Cage

Before going to the Third Optical Device, you can optionally free the Seelie in the other cage. To do this, you need to access a third viewfinder near the entrance of the room. Use it and transfer the energy to the energy cell below.

Once you do, go back to the viewfinder inside and transfer energy to the cell near the cage to unlock it. Once the Seelie is free, follow it towards the next location nearby.

Go to the Other Side of the Room

The Seelie will pass through a barrier and stop, so you have to find another way around. On the other side of the room, you will find a wall with an explosive barrel nearby. Use it to destroy the wall and enter the room.

Beware of the Clockwork Meka inside the room! Take it out first then you can safely follow the Seelie towards its statue. Doing all of this will reward you with a Precious Chest.

Find the Third Optical Device

Follow the beam of light that the second optical device emitted to find the third optical device. It is located on the upper left of the ruins, so glide down and head towards it. The third optical device is also missing a component, so you have to find it.

Take the Component From the Upper Floor

The component is located on the upper floor of the ruin. Just climb the wall nearby and pick it up, then take it back to the third optical device to start calibrating it.

Start the Third Optical Device

You can now start and calibrate the third optical device. This time, there will be three images so you need to calibrate it thrice. Remember to wait for the image to become clear before calibrating it.

Start the Central Optical Device

Once the third optical device is calibrated, head to the middle area and start the central optical device. A short cutscene will play and a metal gate will open below the middle area.

Continue Exploring

Enter the gate below the middle area but beware of the Clockwork Meka. Take them out and proceed further into the cave until you see another door with a switch. Interact with it and head into the next area.

Find the Energy Cell

You will see an inactive terminal and some stationary Clockwork Meka. You have to find the energy cell to make the terminal active. The energy cell is in a destructible rock, just north of the room. Take it and bring it back to the terminal then begin the test.

Defeat Lothair and Claire

Once the test begins, the Clockwork Meka will move and become hostile. Take them out and a cutscene will play, with a person entering the room after the battle.

Talk to Sevigne

Talk to the researcher who just entered the room. She will turn out to be Sevigne, a researcher from the Fontaine Research Institute. She will ask you to find and recover the Punched Tapes within the room next.

Find the Punched Tapes

The Punched Tapes are scattered all over the room. There are only three Punched Tapes, so they should not be too hard to find.

Recover the First Punched Tape

The first Punched Tape is near a big picture frame, just on top of the box with some books on it. Recover it and head to the second Punched Tape.

Recover the Second Punched Tape

The second Punched Tape is in a drawer of a broken closet, near some scattered books. Take it and head to the third Punched Tape.

Recover the Third Punched Tape

The third Punched Tape is on the floor by a bunch of boxes and books. Take it and head back to Sevigne for another dialogue. She will tell you to go to the Fontaine Research Institute to find Chisseray.

Dive Into the Water

After talking with Sevigne, she will tell you to exit the room by using the crack in the floor. Dive in the water and head towards the current in the water.

Use the Current to Exit

Once you see the current, approach it and it will take you back to the open ocean. On the way out, you will also see a Mysterious Ore which you can pick up. Swim up to the surface and head to the Fontaine Research Institute.

Talk to Chisseray

After teleporting to the Fontaine Research Institute, find and talk to Chisseray. Finish the dialogue and this will finish the quest!

Road to the Singularity Rewards

Total Quest Rewards

Total Quest Rewards
Primogem x40	Mystic Enhancement Ore x3	Mora x33000
Hero's Wit x2

Genshin Impact Related Guides

All Quests and Quest Types

All Fontaine World Quests Guide

Fontaine World Quest Guides
A Certain Notice	“Hey, This Isn’t Pumpkin Soup…”	“If She No Longer Dreams of You...”
A Brush of Seafoam and Crimson	A Certain Stamp	A Certain Trifle
A Fontanian Message	A Gradient of Dreams and Ochre	A Letter
An Expected Lie	An Expected Plan	An Eye for An Eye
Ancient Colors	Ann of the Narzissenkreuz	Ann's Story: Prologue
Another Horizon of Adventure	Aqueous Tidemarks	Blue Longing of Heart and Moon
Book of Esoteric Revelations	Both Brains and Brawn	Canticles of Harmony
Cupid's Lover	Danger Lurks Everywhere in Fontaine	Daydreams Beyond Space and Time
Echoes of the Ancient World	Fishing Game	Foggy Forest Path
Fontaine Research Institute Chronicles	For Yesterday and Tomorrow	Fortune Plango Vulnera
Free Verse	Furious Mouth of the Spring	Game of the Rich
Good Stuff, but Terrible Taste	Gradus ad Capitolium	Happy Birthday
Hereafter...	Impromptu Poem of the Crimson Dawn	In Expert Company Part 1
In Expert Company Part 2	In Search of Lost Time	In the Wake of Narcissus
Initial Facts	Kingdom Through the Looking-Glass	Latecoming Homecoming
Leroy	Leroy: Beautiful Friends	Leroy: Dying Flash
Leroy: Firing Squad	Leroy: Hangman's Noose	Leroy: High Noon
Leroy: Queen of the Night's Aria	Leroy: Under Guard	Meteoric Lance
Muse's Mother	Pursuit	Questioning Melusine and Answering Machine
Questions and Answers	Road to the Singularity	Rowboat's Wake
Savior's Wake	Search in the Algae Sea	Self-Automatic Foraging
Seymour's Story: Prologue	Stagnating in the Rubble	Steambird Interview
Still Mouthwatering!	Strange Stone Chronicle	Thalia and Melpomene
The Final Question	The Fountain Flows Again	The Last Day of Remuria
The Lone Phantom Sail	The Narzissenkreuz Adventure	The Red and the Black
The Shadow Over Petrichor	The Three Primary Colors of Solar Corona	The Wild Fairy of Erinnyes
Through the Looking Glass	Treacherous Light of the Depths	Truly Mouthwatering!
Underwater Nocturne	Unfinished Comedy	Unfinished Story
Upon a Flowery Field of Grass	Vagrants and Scamps	Villains
Waking from the Great Dream	Were It So Easy	Where His Life Lies
Wilting Weeping Willow	Wish-Fulfilling Treasure Hunt	Within the Depths of Erinnyes

List of World Quests