To unlock Sea of Bygone Eras in Genshin Impact, you need to follow the permanent progression that controls Sea of Bygone Eras. The Sea of Bygone Eras is the underwater Remuria region reached through the Canticles of Harmony World Quest chain. The region becomes available after progressing through Petrichor, the Faded Castle and Underwater Nocturne.
This guide focuses on the part that usually stops players around Sea of Bygone Eras in Fontaine: the prerequisite, entrance, puzzle or quest flag that the map itself does not explain clearly. It also covers what to check if the expected Sea of Bygone Eras interaction is still missing after you reach the right place.
Unlock Sea of Bygone Eras in Genshin Impact
Image credit: HoYoverse
The most reliable way to unlock Sea of Bygone Eras in Genshin Impact is to clear the prerequisites first and then follow the local route in order. Before travelling across Fontaine for Sea of Bygone Eras, check these conditions so you do not arrive at a locked door, empty cave or inactive mechanism.
- Reach Petrichor in the Nostoi Region.
- Start The Shadow Over Petrichor and follow Osse into the Faded Castle.
- Continue Canticles of Harmony through Underwater Nocturne.
Step-by-step route
- Complete The Shadow Over Petrichor and obtain the fantastical music box.
- Explore the Faded Castle as Canticles of Harmony continues.
- Finish Underwater Nocturne, the second subquest of the chain.
- Follow the quest route into the newly opened Sea of Bygone Eras.
- Activate the first regional waypoint before exploring Remuria more broadly.
Players who want to unlock Sea of Bygone Eras in Genshin Impact should keep the active quest or exploration objective tracked while moving between these steps. Around Sea of Bygone Eras, vertical map layers, hidden cave entrances and state-based mechanics can matter more than horizontal distance, so check the map layer as well as the marker.
The Sea of Bygone Eras is a separate map area with mostly underwater traversal.
The Last Day of Remuria continues the chain deeper into the ancient kingdom after the initial region opens.
Why it can still look locked or incomplete
If you are standing in Petrichor but cannot reach the separate map, continue Canticles of Harmony. The Sea is story-gated and does not open from ordinary Fontaine diving routes.
If you still cannot unlock Sea of Bygone Eras in Genshin Impact, compare your current objective with the prerequisite list before restarting the game. For Sea of Bygone Eras, a missing quest flag is not fixed by repeating the final puzzle, and a hidden entrance will not appear just because the destination icon is visible.
Useful details before you leave the area
The talking cat companion Osse guides the early transition from Petrichor into the submerged ruins.
Once you unlock Sea of Bygone Eras in Genshin Impact, activate the nearest Teleport Waypoint, domain marker or permanent shortcut before moving on. That turns later material farming, quest cleanup and collectible hunting around Sea of Bygone Eras into a short return instead of a repeat of the full unlock route.
Common questions
Why can’t I unlock Sea of Bygone Eras in Genshin Impact?
A good check before you unlock Sea of Bygone Eras in Genshin Impact is whether the named prerequisite has actually completed, not merely started. For Sea of Bygone Eras, also confirm you are on the correct underground or surface map layer and that any required gadget, song, clearance level or regional ability is available.
Is Sea of Bygone Eras permanent?
Yes. Sea of Bygone Eras is part of permanent Fontaine content rather than a limited-time event. Later game updates can adjust interface details around Sea of Bygone Eras, but its underlying quest or exploration route remains available to accounts that have not completed it yet.
What should I do next?
Once inside, activate waypoints as the quest moves through Remuria so later chest and Hydroculus cleanup does not require replaying long underwater corridors.
This route should let you unlock Sea of Bygone Eras in Genshin Impact without relying on unintended shortcuts. For current official notices or future changes affecting Sea of Bygone Eras, use the official Genshin Impact website after you have finished the permanent steps above.
