While doing the Lotus Eater World Quest, you can obtain a Secret Room Key from the Common Chest behind the afterimage of Adonis. It can, in turn, unlock one of Enkanomiya’s hidden ruins. Make sure that the Quest Item is in your Inventory before beginning this puzzle.
Unlocking the Secret Room
Start by heading to The Narrows—in the area circled in the image below—during Whitenight. The place is located on a platform under the cliff, so jump down once you reach the edge to get to the location.
Once you get there, interact with the large door and use the Secret Room Key to unlock it. You’ll find yourself inside a cave-like ruin. Keep going straight, and you’ll find yourself in what seems to be a dead end.
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However, using Elemental Sight will reveal that the stone blocking the way can be broken by hitting the Exploding Barrels. Doing so will open up a path for you to move forward.
Day-Night Switch Puzzle
You’ll encounter two day-night switching mechanisms. There are barriers in front of both of them, indicating that you can only pass during Evernight. Solve this puzzle by doing the following steps in the exact order:
- Interact with day-night switching mechanism A to change Enkanomiya to Evernight.
- Another mechanism will appear. Interact with it to open the gate behind the other barrier.
- Interact with day-night switching mechanism A once again to change the setting to Whitenight.
- Interact with day-night switching mechanism B to change to Evernight.
- Enter the now-open gate, where you’ll find a Mooncrux. Approach the Mooncrux to obtain the blue aura.
- Interact with day-night switching mechanism B once again to change to Whitenight.
Unlocking the Exit Gate
Once that’s done, go down the stairs and you’ll find a broken mechanism. Approach it with the aura of the Mooncrux to reveal a triangular mechanism. Attack the triangular mechanism once to open the gate behind it.
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As you thread into the path opened by the gate, you’ll find a Sunfire Phantasm on the wall to the left. Ignore it for now and proceed to unlock the gate at the edge of the water by interacting with the lever. There’s also a Precious Chest that you can loot.
Keep this gate open and head to the Dainichi Mikoshi to change Enkanomiya back to Whitenight. It’s very important that you use a day-night switching mechanism outside of the ruin, as using the same mechanisms in the prior puzzle will summon a barrier that will block your way.
Once it’s Whitenight, head back to the ruin using the gate above as your entrance. Do not use the front door, or you won’t be able to pass.
The Serpent’s Heart Puzzle
Now that you’re back in the ruin during Whitenight, the Sunfire Phantasm will disappear and turn into symbols. Interact with the wall to light up the symbols and reveal the order for passing through the transparent walls in The Serpent’s Heart.
Head to the clearing in the northwest of The Serpent’s Heart. Make sure that you come prepared with a battle-ready team.
Walk past the transparent walls from the inside out in the same order as the image above. Once all five are done in the right order, a cutscene will play, and three Ruin Graders will spawn. Defeat all three to spawn a Luxurious Chest, completing this puzzle.
Check out our guide on How to complete the Collection of Dragons and Snakes World Quest in Enkanomiya in Genshin Impact to learn more about the last day of Byakuyakoku.