The Luminescent Cavern in Fisch unlocks with 3 specific keystones scattered across 9 island locations. Each player receives a unique keystone combination, requiring you to check the pedestals in Desolate Deep first. This comprehensive guide reveals all keystone coordinates, step-by-step unlocking strategies, and exclusive tips to access the cavern's rare fish and Crimson Cavern progression.
| Keystone Type | Island Location | Coordinates | Difficulty |
|---|---|---|---|
| Sun Keystone | Sunstone Island | (-937, 227, -983) | Easy |
| Turtle Keystone | Terrapin Island | (57, 149, 2033) | Easy |
| Lightning Keystone | Grand Reef | (-3409, 134, 262) | Medium |
| Mushroom Keystone | Mushgrove Swamp | (2666, 130, -717) | Easy |
| Cliff Keystone | Castaway Cliffs | (473, 230, -2159) | Hard |
| Fossil Keystone | Ancient Isle | (6068, 225, 261) | Medium |
| Volcano Keystone | Roslit Bay | (-1970, 175, 268) | Medium |
| Skull Keystone | Forsaken Shores | (-2797, 209, 1542) | Easy |
| Snowflake Keystone | Snowburrow | (2787, 153, 2602) | Hard |
Before hunting for keystones, you must identify which three you need:
Contents
Each player receives a randomized combination of three keystones, making this first step essential for efficient hunting.
Coordinates: (-937, 227, -983)
Location: Inside Merlin's Hut at the island's highest point
Navigation: Climb to the summit of Sunstone Island and enter Merlin's Hut. The keystone sits prominently on a wooden barrel to the right.
Pro Tip: This is the most accessible keystone and perfect for beginners. No special equipment required.
Coordinates: (57, 149, 2033)
Location: Inside Terrapin Hideaway cave
Navigation: Find the cave entrance near the middle of Terrapin Island. Enter the Terrapin Hideaway and proceed to the back room where the keystone glows softly.
Navigation Tip: Look for the darker area against the island's terrain that marks the cave entrance.
Coordinates: (-3409, 134, 262)
Location: Small island left of Shipwright's island
Navigation: Travel to Grand Reef and locate the smallest island near the Shipwright. The keystone rests between two rocks near a bush.
Search Strategy: Use the Shipwright as your reference point and systematically explore the smaller surrounding islands.
Coordinates: (2666, 130, -717)
Location: On top of a boat near the alligator area
Navigation: Head to the alligator abundance area in Mushgrove Swamp. Look for a boat where the Mushroom Keystone sits prominently on top.
Time-Saving Tip: The boat is located near the Shipwright, making it easy to spot once you're in the right area.
Coordinates: (473, 230, -2159)
Location: Hidden gap near the second level ledge
Navigation: This is the most challenging keystone to find. Start at the Shipwright and climb the ladders, but head left instead of right. Continue past the faction leaders and empty house until you reach a campfire NPC. Turn right toward a tree and look for a tiny gap behind it.
Critical Detail: Many players miss this location. The gap is much smaller than expected – look carefully behind the tree at the paved pathway slope.
Coordinates: (6068, 225, 261)
Location: Wooden heap lifted by cranes near the merchant
Navigation: Locate the merchant area at Ancient Isles where you'll find construction equipment. The Fossil Keystone rests on a heap of wood lifted by cranes.
Access Methods:
Coordinates: (-1970, 175, 268)
Location: Center stone inside the volcano
Navigation: Enter the Roslit Volcano and navigate to the central stone platform. The keystone sits dramatically in the middle of the volcano.
Safety Tip: Equip heat resistance gear before entering to avoid damage while collecting the keystone.
Coordinates: (-2797, 209, 1542)
Location: Next to Jack Marrow NPC
Navigation: Visit Forsaken Shores and locate the pirate NPC Jack Marrow (where you fix maps). The orange-colored Skull Keystone sits on the ground next to this NPC on a small cliff.
Landmark Reference: Use the distinctive skull structure near the Shipwright as your navigation point.
Coordinates: (2787, 153, 2602)
Location: Secret cave behind unlocked door
Navigation: This keystone requires solving a puzzle. Travel to Snowcap Island and find the hidden Snowcap Cave entrance at the back of the island.
Puzzle Solution:
Before attempting to unlock the Luminescent Cavern, ensure you have:
Using the coordinates and navigation tips above, collect the three keystones identified by the pedestals in Desolate Deep. Remember the locations are randomized per player.
Important: If you try to place a non-matching keystone, an error message will appear indicating which one is required.
Once the crack opens:
The Luminescent Cavern contains unique fish species with specific bait, time, and season requirements:
The ultimate goal in Luminescent Cavern is progression to Crimson Cavern:
Inside Crimson Cavern, you'll find:
Note: You must complete the shiny sparkling bestiary in Crimson Caverns before claiming the Ruinous Oath rod.
Problem: The keystone doesn't fit when you try to place it.
Solution: This means you have the wrong keystone for that pedestal. Check the error message to see which one is required, or return to the pedestals to refresh your memory of which three you need.
Problem: You're at the right coordinates but can't see the keystone.
Solution:
Problem: All three keystones are placed but the crack won't open.
Solution:
Problem: Attempting to use glitches or exploits to access the cavern.
Solution: Avoid using exploits as they may result in account penalties. Follow the legitimate unlocking process described in this guide for reliable access.
For players looking to optimize their keystone collection time:
If you have multiple characters:
You need exactly 3 keystones out of the 9 available locations. Each player receives a randomized combination, so you must check the pedestals in Desolate Deep first to identify which three you need.
No, the keystone combination is permanently assigned to your character and cannot be changed. You must collect the specific three keystones assigned to you.
No, keystones are one-time collectibles. Once you collect a keystone, it remains in your inventory permanently and cannot be collected again on the same character.
The game will display an error message indicating that the keystone doesn't match the pedestal requirements. Simply try a different keystone until you find the correct one.
No, the Luminescent Cavern is locked behind the keystone puzzle and cannot be accessed through other means. You must collect and place the correct three keystones.
The time varies depending on your familiarity with the islands and equipment quality. On average, expect 1-3 hours to collect all three required keystones, including travel time.
There are no specific level requirements, but having better equipment (flippers, light sources) significantly improves your ability to reach certain keystone locations.
While not strictly required for all locations, having Super Flippers, Water Bubble, and good light sources makes collecting keystones much easier, especially for hard-to-reach locations.
Currently, keystones cannot be traded between players. Each character must collect their own assigned keystones.
Focus on completing the bestiary by catching all unique fish species, particularly the Colossal Blue Dragon, which is essential for progressing to Crimson Cavern and obtaining the Ruinous Oath rod.
The Luminescent Cavern represents one of Fisch's most exciting content updates in 2025, offering players a challenging puzzle to solve followed by rewarding fishing opportunities and progression to the exclusive Crimson Cavern. By following this comprehensive guide, you'll unlock the cavern efficiently and be well-prepared for the challenges and rewards that await within.
Remember to bookmark this guide for quick reference during your keystone hunting journey, and join the official Discord community for real-time discussions with fellow anglers. Happy fishing, and may you catch the legendary Colossal Blue Dragon!
Have you unlocked the Luminescent Cavern yet? Share your experiences and tips in the comments below, and don't forget to check back regularly for updated coordinates and new strategies as the game evolves!