If you’ve been grinding Fisch lately, you’ve probably heard whispers about the keystones and the shiny new Luminescent Cavern. Collecting these little artifacts is the first step toward getting inside the cavern, and eventually facing off with some of the rarest fish in the game, including the colossal blue dragon.
I went through all the spots myself, and trust me, some of them are sneaky. To save you from hours of random rock-hopping, here’s a breakdown of every keystone location in Fisch.
Fisch Keystone Locations Guide
Turtle Keystone
The turtle keystone is on Terapin Island. Near the shipwright, there’s a rock you can hop on. Walk around to the other side and you’ll spot this little cave. They literally stuffed it behind some wood on top of a barrel. It feels like the devs were trolling.
Lightning Keystone
The lightning one is easier. Go to Grand Reef, head to the smallest island on the right. As soon as you land, look between two rocks near a bush. It’s just lying there on the floor, no effort at all. I almost stepped right over it.
Sun Keystone
The sun keystone made me suspicious of every barrel in the game. You go to Sunstone Island, climb up to Merlin’s Hut (ladder, path, left turn). Inside, open the door on the right and yep, barrel again. At this point I was opening barrels like a maniac just in case.
Volcano Keystone
Volcano one sounds epic but it’s boring. Go to Rosid, jump into the volcano, and hop onto the middle island platform. It’s on the ground. That’s it.
Skull Keystone
Skull keystone is at Forsaken Shores. Start near the shipwright, follow the path, climb the ladders, and eventually you’ll reach the skull. The keystone’s on the floor. I thought there’d be some puzzle here, but nope.
Fossil Keystone
The fossil keystone at Ancient Isles actually annoyed me. You either zipline and jump off at the right time (which I failed the first time and had to redo) or climb the ladder and glide across. Once you get there, it’s waiting. Nothing fancy, just a hassle.
Mushroom Keystone
The mushroom one is the most obvious. At Alligator Marsh, there’s a rowboat right by the shipwright. Go inside. That’s it. That’s the whole keystone.
Cliff Keystone
The cliff keystone at Castaway Cliff was the sneaky one. From the shipwright, climb the ladders but don’t go right like you normally would, go left. Keep following the path past the faction leaders and the empty house. Near a campfire NPC, turn right toward a tree. There’s a tiny gap behind it. I walked past this spot like three times before realizing it. Keystone’s back there.
Snowflake Keystone
The snowflake keystone is actually cool. Head to Snow Cap, then Snow Burrow. Inside a hidden cave, climb the ladder. You’ll see three cracks in the wall. Click the top, left, and bottom ones quickly, and a secret door opens up. Inside is a campfire area, climb up again and boom, there’s the snowflake keystone. This one at least feels like an actual puzzle.
Once you’ve got your keystones, here’s the part that matters. You only need three specific ones, but most people just grab them all. Make sure you’re geared: water bubble, super flippers, and something that lights up the dark. Fairy works, or the lantern. I cranked up my brightness in settings too, otherwise you’re basically blind.
Head to Desolate Deep. There are pedestals there. Hold your keystone, slot it in, and do that for all three. The wall cracks open like something out of an adventure movie. Step through, and you’re in the Mysterious River. Either raft down or walk along the side until you reach the cavern entrance.
And then you’re finally in the Luminescent Cavern. The whole place glows, and it’s where you find the colossal blue dragon. Don’t expect it to spawn right away though. You usually have to wait for a hunt event, and it shows up near the corners. The first time I saw it I literally froze because the thing is massive.
If you’re on the “Mutated Dragon” quest, you need the crimson mutated version. Catching that unlocks Crimson Cavern, which is basically Fisch saying “welcome to endgame.” NPCs, puzzles with crystals, all that. And the big reward there is the Ruinous Oath, which costs 30 million and insane grinding because you also have to finish the shiny bestiary in there.