Back in 2026, the Firework Isles in Infinity Nikki still hold their timeless charm, with adventurers flocking to uncover their hidden treasures. Among the four mysterious caverns scattered across the isles, the Behind-the-Mountain Cavern stands as a classic puzzle waiting to be solved. While the Gloomy Cavern might steal the spotlight as the first stop on the main quest, this particular cavern offers its own brand of quiet, rewarding challenge for stylists who venture off the beaten path. It's the kind of place that whispers secrets to those patient enough to listen, tucked away just north of the serene Clearheart Lake. The journey there feels like stepping into a living painting, where every hill and ripple of water tells a story.

The key to unlocking this stony sanctuary is, as veterans know, all about the fireworks. The cavern's entrance, guarded by a silent, locked gate, isn't just being stubborn—it's waiting for a specific ceremonial light show. Right beside it, a weathered stone slab acts as the ancient instruction manual. Interacting with it reveals a map that's more of a gentle nudge than a detailed guide. It points to the cavern itself and marks the general locations of three special fireworks that need a personal touch to awaken. Honestly, it's like the game is saying, 'Here's the idea, now go figure out the details!' The mechanism is a signature of the Firework Isles' caverns: find three, light three, gain entry. Simple on paper, but the isles always have a way of making you work for it.

Now, for the real adventure—the scavenger hunt. The first firework isn't too far. From the high vantage point of the Fireworks Peak Warp Spire, the world stretches out below. A glide eastwards, catching the thermal currents, brings you to a lower hill where the first firework rests, almost shyly. It's a straightforward start, a chance to stretch your wings before the puzzle gets real.

The second target asks for a bit more grace. Teleporting to the Crescent Shoal Warp Spire changes the scenery entirely—water replaces rock. Looking southeast, the firework sits proudly on one of the distant Relic Isles. Getting there is a mini-platforming challenge, hopping across broken pillars and ancient platforms that jut out of the water like forgotten stepping stones. Once you finally reach it, it's time for the main event: equipping the 'Fiery Glow' outfit ability. Channeling that power to activate the firework never gets old; it’s that perfect mix of style and substance the game is famous for.

The third and final firework adds a dash of excitement. Heading to the Songbreeze Highland Foothills Warp Spire and moving southeast into the forest, the atmosphere shifts. The area isn't always peaceful—it's often patrolled by Esselings. So, it’s a two-step process: clear out any playful (or not-so-playful) enemies guarding the area, then calmly walk up and ignite the last firework. It's a nice little reminder that in Infinity Nikki, even a treasure hunt might involve a quick fashion-focused skirmish.

With all three fireworks painting the sky with their silent, magical light, the journey circles back. Returning to the Behind-the-Mountain Cavern reveals the once-locked gate now invitingly open. Inside, the reward is immediate and satisfying: a room brimming with treasure chests. The loot breakdown is pretty sweet:

Reward Type	Quantity	Details
Diamond Chests (5 Diamonds)	Multiple	Scattered around the room for that satisfying multi-open feel.
Large Diamond Chest (30 Diamonds)	1	The star prize, waiting to be found.
Dew of Firework	A couple	Special collectibles with their own purpose.
Whim Balloon	1	A quirky find for a special friend.

Unlike some caverns that lead to deeper mysteries, this one is a delightful dead end—a cozy, treasure-filled room that says, 'This is it, and isn't it great?' But the rewards don't stop at diamonds. Scattered inside are a couple of Dew of Firework, glowing with potential. These aren't just for show; they're currency for the beloved NPC Vita over on Sparkheart Island, who always has something interesting to trade. And let's not forget the Whim Balloon—a playful, floating oddity that Vita also happily accepts, exchanging it for sketches, more diamonds, and other goodies. It’s these layers of reward that make the trip worthwhile.

So, for any stylist looking for a self-contained adventure on the Firework Isles, the Behind-the-Mountain Cavern is a perfect choice. It’s a puzzle that respects your time, a hunt with clear goals, and a payoff that fuels both your wardrobe and your wanderlust. In the ever-evolving world of Infinity Nikki, some classics just don't need to change.