Usopp has never told a horror story.

"Come on, this way, this way!" "Go faster, we don't have time for this!" "Oh- God!"

If you asked him why not he'd tell you, as a joke, that he had no experience with horror, everything he'd ever done had resulted in ineffable success, fame, fortune and, on occasion, rainbows.

The halls are tight and have low ceilings, the walls have long streaks on them, drip stains. He half expects stalagmites. There's a weight in the air, humidity that's cool, even the air is wet. The darkness makes the hall seem smaller, and it doesn't help that they'd snagged lanterns from the supply rack at the entrance, not when the lanterns are lit by a luminescent rock nailed into the center of the domed glass.

He'd then tell you seriously that he simply didn't favor the genre, it took a lot less finesse to move things along, a simple recipe. Take people, put them in a closed space, add scary stuff. He liked to think he was above it, it was just too easy.

They hear the water before they see it, rushing water and panic seizes up in Usopp's chest. Zoro makes an audible sound of anger and frustration. Usopp can't really believe it, that him and Zoro are the last chance. Their guide and Nami had both stopped back a ways, to keep anyone from following. They'd heard people following.

This is only partially true.

Zoro skids to a stop in front of him, holding his hands out, swords in hand as he grips the walls on either side, looking for traction as the ground becomes slippery. "Zoro!" Usopp yelps and thuds right into the swordsman's back, pushing the both of them through the entryway that Zoro had been trying to prevent passing over, they lurch forward, Zoro breaks the force of the fall for Usopp, but he can still tell they fell a few meters at least, and have splashed down in a shallow pool of water, a few feet deep. The lantern's broken.

It is just too easy, it runs through his mind almost every second of the day after all. It's an essential part of human nature to write horror stories; it's called fear.

Usopp scrambles to his feet and fumbles through the water, sloshing around as he searches for his slingshot, he'd been holding it, but he'd dropped it. Zoro pulls himself straight up and spits to the side, readjusting his grip on his swords, staring out into the dark. It's very dark. Usopp's hand brushes the lantern, the glass has broken, but the light is still going, muted by the water it's under. He should have picked it up first.

Fight or flight, that tickle up one's spine when they feel something foreboding, hair-raising. Chilling. He's never understood how anyone could stand thriller movies, or thriller rides, weren't there enough horrors in life? Monsters and villains and horrible, horrible accidents? Wasn't there enough bad?

His fingers wrap around the craggy edges and smooth facets of the light and he pulls it out, the water peeling away from his skin and splashing back down in a cacophony that echoes. Light in hand he straightens, and a green-blue sheen is cast over the nearest features of what is apparently a large cavern; uneven edges to rock pillars nearby, some kind of murk in the water that he hadn't noticed before, a heavy mist that rests just above their heads.

But it's true. It's human nature to have fear and to think about it, hold it close in an attempt to understand it.

Zoro steps forward and Usopp moves with him, scooping his slingshot from the water where he now sees it. Zoro shifts slightly and now the metal clink of his scabbards clacking together rings loudly through the cavern, too loud to be natural, too loud to be right. "Zoro…" He whispers and Zoro snarls wordlessly under his breath. Be quiet. They stand stock still, listening, waiting, the only sound he can pick out is their breath and the blood rushing through his ears as his heart rate begins to accelerate. Doomsday scenarios playing merrily through his mind. 'It's a cavern of horrors,' she'd said.

Usopp likes to say that curiosity killed the cat. He'd rather keep his fear locked away inside himself. Which he does.

'We've seen scary stuff before,' Nami had assured her and the guide had shook her head, long ribbons and clips bouncing around as her hair came looser and looser from its bun. 'Not like this, never like this. It takes what you fear most…' 'A guard? We'll beat it. It's not a choice.' Zoro broke in and their guide seems exasperated and fearful. 'Not a guard, an… essence. There's a reason this island doesn't have a village, just a pirate crew's operational base. This place is why. It's not your fears, not really, it's, it's not just you. It's everyone, everyone's fears, but fears isn't the right word, it's not… definable. It's primal.' Zoro doesn't blink, doesn't even look at her, repeats what matters. 'It's not a choice.' The truth is there, they can't leave, not without facing this, not without getting them back.

The truth is he's written a thousand horror stories.

They exist in his head. They're intimate, a man's greatest fears.

And there, the noise they hadn't been able to hear rises into a roar, dips into a wail, maintains a steady keen. Usopp's shaking in his boots, Zoro's tense, coiled, ready to spring. The water ripples as something within it moves, it no longer looks hazy, but dark, something is clouding it. 'Zoro, the water!" Usopp shrieks and scurries up the side of the nearest rock pillar, clutching, pulling himself to a skinny lip, Zoro digs a blade into the stone and uses it as a handhold, beneath them the water begins to roil, the dark substance churning. Zoro curses while Usopp reaches higher and pulls himself up through the bottom of the fog, hoisting himself onto the top of the stone pillar, balancing on the pinnacle. It's the shortest he can see, because above the fog he can see a lot more. Scores of them, tall and short and filling the cavern which he can't see the far wall of, it's too full. The pillars, they're stalagmites, there are stalactites too, hanging just above all of them, some really are pillars, stalagmites and stalactites connected, in the center there are cages. In the center there are skeletons.

The truth is none of them were any good.

'Zoro,' he whispers and the swordsman grunts, climbing up beside him, staring out at the cavern with clenched teeth. Something moves, and from nothing there's something, from utter blackness, a dark smudge on the overall gray color scheme of the cavern, and it morphs into something languid and sinuous. It rears, the dark shape, without true form and lurches outward, the wail, the roar, the keen, it comes from there. And there is another, a howl, and it is human, and it is Chopper. Usopp clutches at Zoro's arm as the swordsman lets out a string of curses, the beast swipes at something, there is a heavy stench that fills the cavern, Usopp cringes, it smells of mushrooms and blood. A musky scent that has a tinge of fresh frost mixed in. Gritting his teeth, Usopp stretches out and jumps onto the nearest pillar, this one is more craggy than the other ones within jumping distance. Usopp doesn't climb too high because this is a column, it joins with a stalactite, and where they join is a gnarled knot of stone, in the center of which he can see dull flashes of white, and the flickering glow of a green light.

Because seeing... This, he supposes is the best thing to call it. This.

Zoro is gone now, Usopp isn't sure where, he hasn't been able to take his eyes off the creature, no, the essence. It's not alive, it can't be, it isn't. Zoro ran off, probably to attack it, he'll show up in a second, unless he got lost. Usopp will take care of their nakama, the devil fruit users who were stashed down here, because suddenly they're too good for sea stone. He heard Chopper, but the sound echoed, he's not sure where they are, near the back, he assumes, because it's a long way off. He checks every one because it's hard to tell which skeletons are old prisoners and which one is Brook. They all have glowing green stones trapped within the finger bones of their hands. It makes Usopp want to throw his light away. He doesn't.

It makes him realize that he doesn't actually know what fear is, what something truly scary is.

He's crossed the room, the essence is different now, not black but red, hot and bubbling with a churning well of hot colors, emanating heat that dribbles down it's side and makes the water steam. He can hear Luffy shouting, angry. The magma surges, Zoro strikes, the fog thickens, Usopp files. He's found her, Robin, nestled into the farthest corner of her column prison, the glowing stone held close to her face, her lips are moving like she's praying, Usopp is filing quietly away at the thinnest bar of her prison. She is pale and her hair is ratty, they've been in here a day or so but she looks like a hermit, condemned to solitude for decades, centuries, she doesn't stir when he calls. Chopper's prison is a few columns away, Usopp hadn't looked yet, he wanted to get Robin out, she could help him cross the pillars, or at least she could get out. Chopper's talking to himself, but Usopp can't understand it, it's gibberish, spoken quickly, desperately, questions without answers, statements without fact. Usopp files.

Unspeakable.

He's moved on to Chopper now, Robin didn't wake up, he left her on top of a flatter stalagmite, the point broken off. Chopper's is easier to break, he snaps a couple of the stone bars but Chopper himself is the problem. He's not unresponsive, like Robin, he roars at Usopp and shifts into heavy point, smashing out at the sniper and breaking a few more bars, but he circles, does not come out, Usopp curses at him. His hair is matted, tufts missing, blood drizzling from a scrape on his snout. 'Get away!' He shrieks, kicking out with his hooves, he's being too loud, Zoro isn't as loud fighting the essence, Luffy's gone quiet, Usopp is scared.

Nothing is as horrifying as reality. Truth is stranger than fiction? He wishes his horror stories could have stayed in his head, where he tried so hard to keep them.

Zoro's beaten it, he's pretty sure. There's no more fighting, Luffy's laughing, he thinks that's what that sound is. Usopp's looking for Brook now, but he's not sure he can find it. It'd be easier if Chopper could catch his scent, but Chopper isn't talking anymore, just turning wild circles and moaning. Luffy's stopped laughing, Chopper's stopped moaning, he hears Zoro shout, Brook begins to croon, things are getting crazy. Usopp slams his hands over his ears and jumps to the next pillar.

Where he'd thought he'd kept them.

The lights went out. The stones went dark and Usopp doesn't know where he is, where they are, he can't hear, he can't see, he can feel, only with his fear. The hairs on the back of his neck are prickling, his hands shake as he rummages through his bag, looking for one of his old fire stars, to wish away the dark, to give him a few seconds to find Robin. He can get her out, if he can find her. Maybe he can find a new stone, maybe Chopper will follow him, maybe Luffy is about to break free, he just needs a little light. His fingers rub at something flaky in his bag, a round pellet that smells of gun powder when he holds it to his nose, he grins shakily, sets it on the rock lip he's crouched on, and smashes down with another rock, the fire flares. He yelps, just in front of him is the essence, hollow eyes and fleshy lips, burns dripping magma from one side of it's face, sharp teeth that snarl and glisten, purple spittle sizzling as it touches the rock. Intelligence and hatred glowing from within the hollow eyes. The fire goes out.

Guess not.