Sinthe Headquarters Domain Walkthrough – As Light Rain Falls Without Reason (Genshin Impact)

The Genshin Impact Fontaine Archon Quest Chapter IV: Act II - As Light Rain Falls Without Reason begins immediately after winning the trial against Furina, and sees you closing in on an old case surrounding the incorrect judgment laid upon Navia's father. In this Archon Quest, you'll be helping Navia investigate key suspects who may have to do with the Sinthe epidemic in the Spina di Rosula and its connection with the disappearing girls.

While Navia runs to the Opera Epiclese to defend the wrongly-accused Childe, you and Paimon must investigate the Sinthe Headquarters underwater to find evidence to present in court.

All Sinthe Production Base Puzzle Solutions & Chest Locations in Genshin Impact

The Sinthe Headquarters is considered a Domain, so you can't return after leaving. Follow this walkthrough from start to end to ensure you don't miss out on any of the Chests. Before starting, make sure you're familiar with all diving controls as well.

Once you're prompted to investigate the Sinthe production base, ascend in the water until your character is swimming, then swim toward land. Follow the path to proceed deeper inside the Domain, where you'll encounter a Door of Resurrection that can be used to configure your party setup. I recommend bringing your DPS team, as you need to defeat enemies inside.

Once inside, defeat all the enemies to unlock the mechanism at the center of the clearing, then interact with the mechanism to elevate the ground level. Once the platform stops ascending, you can continue onward.

Related: How to unlock the underground Teleport Waypoint in the Court of Fontaine in Genshin Impact

The door leading further into the headquarters will automatically open, so you can continue without getting a key. Don't forget to claim the Common Chest beside it, as you won't be able to return for it later.

You'll be met with a dead end, so you need to jump down to start swimming, then dive underwater using the walk/run switch (Left Ctrl for PC).

Once underwater, you'll encounter marine creatures with shield icons over their heads. Press and hold the Normal Attack button to target any of the creatures, then release it to absorb their ability. An E skill should appear on the bottom right of your screen. If it's not appearing, try again.

Approach the cracked wall (pictured above) and use the skill you just absorbed by clicking on the Elemental Skill button. Doing so will prompt the wall to shatter, allowing you to explore further inside. You'll find yourself inside a small room, where you must ascend and swim toward the mechanism on land.

Interact with the mechanism (pictured above) to prompt the water level to go up. You'll find yourself submerged underwater again, so ascend one more time until you're swimming instead of diving.

Swim toward the open door. It's hard to miss, but if you can't find it, turn on the quest navigator to avoid getting lost. Once inside, follow the path forward until you reach the clearing filled with enemies.

Related: The First Great Magic – How to get, Ascension, stats, and who can use it in Genshin Impact

Head toward the clearing and defeat all the enemies to unlock the Exquisite Chest. Don't forget to loot it now, as you won't be able to return for it later. When you're done, interact with the nearby mechanism to raise the water level one more time. After the small cutscene, you'll find yourself submerged underwater, so ascend until you're swimming.

Swim toward the tunnel pictured above (use the quest navigator if you can't find it) and follow the path forward. You'll find a large opening on the ground, so plunge downward to proceed. Follow the path until you enter a room.

Inside the room, the first thing you must do is loot the Common Chest. Again, don't forget to do this as you can't come back for it later. After looting, interact with the mechanism to open the door behind it.

Once the door is open, wait for a bridge to form so you can reach the room on the opposite side. Cross the bridge to find a clearing will with enemies. While there are no Chest rewards, you need to defeat the enemies to open a path forward.

After defeating the enemies, follow the path toward the newly-opened door. Glide or plunge downward, then go through the arch to trigger a cutscene and dialogue with Paimon. At this point you've entered the Sinthe laboratory, so you can commence the actual investigation.

While investigating, you'll only be able to control Aether or Lumine. Click on the Elemental Skill button to prompt magnifying glasses to appear throughout the area. The magnifying glasses will only appear for a few seconds, but you can keep pressing the Elemental Skill button to make them appear again.

Interact with the objects marked with magnifying glasses to examine them and obtain evidence. You need to acquire all of the following:

Once you've obtained all of the evidence above (in any order), the game will automatically trigger dialogue with Paimon, at which time you need to find one last piece of evidence to solve the final piece of the puzzle. Examine Miscellaneous Objects one more time to discover Vigneire's Notebook. After this segment, you'll be teleported to the Opera Epiclese, where you must help Navia win the case.

For more Fontaine guides, check out How to farm Emperor’s Resolution & find the Emperor of Fire and Iron in Genshin Impact and All Beryl Conch locations in Genshin Impact here on Pro Game Guides.