In the latest Fisch Update, the developers have added a new POI called Cultist Lair, where players can catch new exclusive fish, craft rods, and participate in various quests. However, reaching this location is quite tricky and requires you to solve a unique task. So, if you are one of those players who are struggling to enter the Cultist Lair, here is a dedicated guide about it.
Where is the Cultist Lair in Fisch?

The Cultist Lair is a secret area in Fisch accessible from Terrapin Island (-200, 130, 1925). But to open it, you must first meet the Sea Traveler NPC on the same island at the backside of the map near the secret bunker. He wears a green dress and looks confused. Interact with him, and he will ask you for a Sea Turtle.

The Sea Turtle is a mythical fish that players can catch on the same Terrapin Island under the following conditions.
- Weather: None
- Time: Day
- Season: None
- Bait: None
I recommend using something like the Steady, Rod of Depths, or Zeus Rod for easily acquiring this fish. Also, if you are unlucky, I recommend fishing in the morning hours. Give the Sea Turtle back to Sea Traveler to get the Sea Traveler Note, which has the following GPS X:0, Y: 155, Z:2000.

This is nothing but the location of a small cave on Terrapin Island called Terrapin Hideaway. There, you will find a small green lever. Pull it to open a secret opening on the left side. Enter through it to reach the Cultist Lair.

This secret lever won't spawn if you don't give the Sea Turtle fish to the Sea Traveler. However, if one of your friends does have the note, you can enter the Cultist Lair along with them while pulling the lever.

Another critical point to note is that the lever will only spawn during a Foggy Night. If you don't have these conditions, I recommend using the Sundial and Smokescreen Totems to fulfill the Weather requirements. For the Sundial Totem, go to the Sunstone Island, and for the Smokescreen, make your way to the Mushgrove Swamp.
Cultist Lair FAQS
No, there is no level requirement to enter the Cultist Lair in Fisch. If you are in the lower levels and want to join the area, I recommend joining with a friend with a higher level.
The only requirement to get a Sea Turtle in Fisch is to fish during the morning hours. So, please wait until the server turns to morning, then start fishing for it with a high-level rod like Rod of Depths, Zeus, or something with a good Luck Rating.
The main reason why the Cultist Lair Lever does not spawn in Fisch is due to the wrong weather requirements. The lever will only spawn during a Foggy Night. Use the Smokescreen and Sundial Totems to get the required weather conditions.
For more on Fisch, check out Complete Fisch Atlantis Guide or Complete Fisch Poseidon Temple Trial Guide