Screenshot by Creamofgames
By completing the Lotus Eater World quest, you can get a secret room key from the common chest behind Adonis' afterimage. He can, in turn, unlock one of Enkanomiya's hidden ruins. Make sure the quest item is in your inventory before starting this puzzle.
Unlock the secret room
Start by going to The Narrows, in the area circled in the image below, during Whitenight. The location is located on a platform under the cliff, so jump down once you reach the edge to get to the location.
Screenshot by Creamofgames
Once there, interact with the large door and use the secret room key to unlock it. You will find yourself inside a cave-like ruin. Keep going straight and you will come to what appears to be a dead end.
Related: Where to Find Ghostfish in Enkanomiya | Genshin Impact
Screenshot by Creamofgames
However, using Elemental Sight will reveal that the stone blocking the path can be shattered by hitting the explosive barrels. This will pave the way for you to move forward.
Day-Night Switch Puzzle
Screenshot by Creamofgames
You will come across two day-night switching mechanisms. There are barriers in front of both, indicating that you can only pass during Evernight. Solve this puzzle by performing the following steps in exact order:
Unlocking the exit door
Screenshot by Creamofgames
Once done, go down the stairs and you will find a broken mechanism. Approach with the aura of the Mooncrux to reveal a triangular mechanism. Attack the triangle mechanism once to open the door behind it.
Related: Where To Find The Afterimages Of The Seven Children Of The Sun In Enkanomiya In Genshin Impact
Screenshot by Creamofgames
Sneaking through the path opened by the door, you'll find a solar fire fantasy on the wall to the left. Ignore it for now and proceed to unlock the waterside door by interacting with the lever. There is also a valuable chest you can pick up.
Keep this door open and head to the Dainichi Mikoshi to change Enkanomiya to Whitenight. It is very important that you use a day-night switch mechanism outside the ruin, because using the same mechanisms in the previous puzzle will summon a barrier that will block your path.
Once it's Whitenight, return to the ruin using the door above as an entrance. Don't use the front door or you won't be able to get through.
The Serpent's Heart Puzzle
Screenshot by Creamofgames
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 of passage through the transparent walls of the Heart of the Serpent.
Screenshot by Creamofgames
Head to the clearing northwest of Serpent's Heart. Be sure to gear up with a battle-ready team.
Walk past the transparent interior walls in the same order as the image above. Once all five are completed in the correct order, a cutscene will play and three Ruin Graders will appear. Defeat all three to spawn a Luxurious Chest and complete this puzzle.
Check out our guide on how to complete the Dragon and Serpent Collection World Quest in Enkanomiya in Genshin Impact for more on Byakuyakoku's Last Day.
