AN: See bottom for more notes.

Disclaimer: I don't own Blue Exorcist or Percy Jackson.

Hell.

A place that is said to be full of fire and brimstone. Where the bad people in the world go to be tortured eternally for all of their misdeeds. Honestly, if people think that idea was bad, Tartarus is worse. In order to compare the two, Percy would buy a microwave of evil, put it on its evilest setting and shove that idea in it. Heat it up for the longest setting plausible, twice. After doing that for a thousand years or so, take it out and you see this despicable thing that even monsters will find terrible. Because anyone else who eats it would be dead.

Then multiply that horribleness by ten and you get Tartarus. Everything about Tartarus tries to kill you. The rivers, the monsters, heck, even the air was some sort of deadly poison that some monster kid bought from a cheap monster supermarket.

(Percy knew that made absolutely no sense, but he was feeling particularly more 'seaweed-brained' than usual)

Percy moved his unwilling limbs as fast as possible. The Death Mist required the person it was round to be close to death in order for it to actually shield that person from monsters. Not to brag or anything, but the son of Poseidon was pretty sure the moment he jumped into Tartarus after the love of his life, he was automatically placed in the category of 'imminent death approaches.'

But no. That wasn't enough. Now Percy certainly fell under the category of 'certain death but because of that I'm somehow safe. . .?' It made a little sense but that's enough sense for him.

Percy's sides heaved and he could faintly hear Annabeth's ragged breath beside his. Their footsteps echoed through the pitch black darkness; Percy was sure that even if they did have their eyes open, they wouldn't be able to see anything through the thick blanket of black that wasn't nearly as comforting as a blanket should be.

The duo's whole experience in Tartarus involved some inescapable heat, but here the heat seemed to be lacking. As if the darkness that came with the House of Nyx chilled their very souls. Percy certainly felt shivers going up his spine. Maybe it was dread, because his skin certainly didn't feel any less scorched than it had earlier.

Pain shuddered through his body as his breath hitched. Percy managed to stop a coughing fit. It wouldn't be any good to alert any monsters to their position, especially sense the whole 'death mist' trick might not actually work.

Percy knew he was running on empty. It was a feeling he had felt so many times before, in so many other desperate situations. He could definitely say this took the cake (though he didn't really have the mental capacity at the moment to relive his whole life story).

He was tired. Mentally, physically, emotionally. There was no denying it, no escaping the facts. He knew Annabeth was feeling the same way. Somewhere, there was a voice whispering in his ear, saying, 'just stop,' and 'it'll be so much easier to give up.' Sometimes it feels so tempting to just lie down and take a nap.

But he knows if he does he won't have the strength to get back up and keep fighting.

He can't just stop fighting, because then he'd be abandoning Annabeth to make it to the Doors of Death alone. And if they both failed, he'd be abandoning his friends to fight the rest of the war on their own.

Loyalty was Percy Jackson's fatal flaw for a reason.

. . .

Fire is a strange thing.

It is a contradictory thing: bringing warmth and comfort, yet becoming a destructive force when not handled cautiously. It sustains life, draws it in, but when one gets too close, they burn. Its deception lures others in and they burn like a moth attracted to a flame.

It is spontaneous, causing uncontrollable flames to spring up from even a hot ash. People have to stomp out any and all sparks in order to prevent disaster.

The symbolism in the Star Wars movies is spot on. A figure draped in shadow snorted. The rebellion being built off a spark of hope, that was stocked. If the Empire was the foolish human who underestimated the flames of rebellion. They ignored the smoke, thinking it was nothing.

Only to have their whole house to burn down when it spread, blowing up their Death Star. A flicker of blue flames escaped their nostrils as their lips spread into a mad grin, showing off sharp, white canines.

They'll make a mistake.

Doesn't have to be a big one. All I need is a tiny bit of leeway. A single breath of air to fuel my flames. They wheezed, suppressing a snicker. It didn't work.

Then I'll burn their life to ashes and let them scatter in the wind.

. . .

It was getting colder.

Percy briefly wondered if they made a wrong turn in the House of Nyx, because it wasn't nearly as dark as it was before (even if he was a seaweed brain, he knew they had already left the literal 'house of darkness') but he figured that it would warm back up to nigh unbearable temperatures the moment they left the place devoid of light.

It didn't, and he was left shivering, goosebumps lining his arms and legs. He had already been getting accustomed to the unbearable heat (it was still unbearable, but after a few days it felt more like a typical Arizona summer, instead of 'congratulations, it is now the hottest day in the hottest place on Earth.'), but now it felt like he just got shoved in a freezer.

Percy grit his teeth together to stop them from chattering.

His seafoam green gaze flitted around nervously, taking in every crevice in the tunnel wall as he cautiously walked forward with Annabeth. The underground passage they found themselves in was small, cramped, not to mention the walls were glistening with some kind of frozen moisture. He was walking shoulder to shoulder with Annabeth, with a slightly crouched posture.

They were both tense. Walking towards the next unknown danger tends to do that to people, especially since there was certain danger behind them. It didn't help that if some random monster came strolling down the tunnel, The duo was practically doomed- there wasn't much space to fight and maneuver in the tight space so it would be hard to incapacitate any monster before they would sound the alarm.

Percy reached down and squeezed Annabeth's hand. She gave a brief squeeze back, but made no move to release his hand. Percy gave a near silent sigh, finding comfort with the contact. He rolled his shoulders, working out a few sore kinks.

The tunnel was getting wider now, gradually opening up to a new cavern. Annabeth glanced over at Percy in the dim, blue light. Careful, she warned him. Normally, in any other life and death situation, Percy would roll his eyes sarcastically. Now all he seemed he could do is nod stoically, eyes void of any humor.

With the agreement, they slowly crept into the open chamber, making sure to avoid scuffing shoes or kicking any stray pebbles. There was a certain foreboding feeling that permuted through both demigods very core, a feeling of wrong, something that contrasted against their own being. A shudder simultaneously passed through both their bodies. Slowly, Percy prepared Riptide to be uncapped; Annabeth held her drakon bone sword at the ready.

They had learned the hard way to trust their gut feelings.

The cavern was large. It had a majorly dome-esque shape, but in the middle of the ceiling there was a hole opening to the sky, allowing little light in. The walls were covered in the cold crystals (Percy would like to call it ice, but it was most likely the Tartarus ripoff of ice that wanted to kill you). The 'ice' gave off wispy mist. Percy shivered, hoping that it wasn't some type of poisonous gas. The floor was reminiscent of a crater, but descended choppily, not smoothly.

In the absolutely middle of the cavern, under the skylight and sitting in the middle of the crater floor, was a cage. It had gothic styling, similar to those fences at stereotypical haunted houses, and had the general shape of a cone- wide at the base and circular, only to narrow the higher up until it became a point. Except, instead of becoming a point it widens back out, in the end looking vaguely like an hourglass, but with a skinnier top. On the floor, there were strange runes encircling the gothic, hourglass, cage.

Then Percy caught sight of the person inside the cage.

He appeared human, if you ignored the odd hair color and strange, winding tail. On his back was an empty sword sheath, while the hilt in his hand only seemed to have half the blade of an average sword. He couldn't be older than fifteen, but Percy had a feeling that this was one of those times where appearances were deceiving.

His clothes were dirty, hardly recognizable, and in tatters- filled with tears and cuts and burn marks. The boy's back was turned to them and he was on his knees, head tilted to the skylight, arms splayed out behind him.

A quiet wheeze left the boy's lips. Then he spoke, his voice raspy, hardly even audible. "Watashi wa anata ga koko ni iru koto o shitte imasu. Watashi o yashinau tame ni koko ni iru nonara, isoide."

He spoke in a foreign dialect, one that sounded mildly Asian in origin. Percy shot a confused glance over to Annabeth. She mouthed, Japanese. Her brow was furrowed, as if trying to work out some puzzle.

The boy paused, then growled when he didn't get a response. "Soretomo, anata wa koko de mokku suru nodesu ka?!"

Annabeth opened her mouth and Percy shot her a warning glance. Do we really need to confront him?

We need all the help we can get. Besides, if he's untrustworthy, then we won't help him out.

Percy gave her a confused look. How do you know he wants our help.

She rolled her eyes. He's in a cage, once he realises we aren't his captors, he'll want us to help him.

She cleared her throat. "Do you know English, or maybe Ancient Greek?"

The boy was silent for a moment, giving out a confused grunt. Then he let out a cough. Slowly, he struggled to his feet, before he turned around. Percy stiffened. The boy was pale, unhealthily pale, and gaunt. His eyes have large bags underneath and the sunken look made his unnatural eyes stand out even more. The pupils were replaced with red slits, surrounded by bright blue, bordering on cerulean irises.

Then his eyes landed on the duo. His mouth dropped open, showing the tips of pearly white fangs. His eyes widened. The broken sword fell from his grip, clattering uselessly to the cold ground. Then he regained focus. A weak grin replaced his gobsmacked expression.

He cleared his throat. "What humans doing in this Jigoku?" His accent was thick, and he stumbled on a few words but the general meaning managed to make it past the language barrier.

Percy spoke up this time. "We fell."

"Obviously." The monster rolled his eyes. "I mean how you make this far?"

Percy didn't really know how to answer that one. Luckily Annabeth did so for him. "A mix of luck, skill, and a plan."

The boy was silent for a few moments. "You have lot of luck. I . . . should ce-cele," he scowled, " honor you. Getting to Doors of Death. I think not you make it through them. just luck, skill, and plan. You need power."

Annabeth narrowed her eyes. "What are you suggesting?"

The boy shrugged. "I locked here for reason."

"Elaborate," she commanded. His brow furrowed at the word. "Explain," she cleared up.

"Demons wanted to control me," he started. Demons? Does he mean monsters, or some other immortal being? "I said no. They must have considered me thr-thre, bad news if they locked me up." His brow furrowed as he mouthed through the sentence. Then he helpfully added, "Bad news for them."

"And who are you?"

He froze. "Okumura Rin. S-son of-" he stopped himself short, only to continue in his native dialect, "Yami no musuko."

Annabeth's stormy grey eyes stared unblinkingly at him, dissecting his every movement. Then she blinked, glancing over at Percy. He isn't telling the whole truth, her eyes managed to convey.

So if we set him free he'll probably betray us at some point?

Most likely.

Annabeth cleared her throat. "What exactly do you want with us?"

Rin's eyes were begging. "Free me. I help you. We go own ways."

"How exactly do I free you?" Annabeth questioned. The cold crystals lining the walls might have something to do with dampening his power (or they were just something to torture him), but the bars of his cage seemed to be made from Stygian Iron. Those definitely would hold anyone back physically, but the runes on the floor most likely would be the easiest to disrupt. Annabeth stared at each one with a critical eye, memorizing them along with their sequence in the overall pattern.

"All have do is mess up the marks," he explained, gesturing to the floor. "My powers will fast end cage." Rin grinned, an unnerving glint in his eye.

Percy and Annabeth shared another look.

He's strong enough to break Stygian Iron. He could be helpfull, Percy managed to convey.

Annabeth shook her head. He's too big of a wild card.

He obviously has a grudge against the monsters. He could help, Percy argued.

Annabeth glared. It could be an act. He could be insane. He might turn on us the moment he destroys the monsters. He already said he doesn't like being controlled; what do you think the gods will do to a powerful person who can't be controlled?

Percy sighed in resignation. He'll hate us.

Annabeth nodded. He'll hate us in prison or he'll be the next one to try to overthrow the gods.

The monster in question raised a brow at the prolonged eye contact and his head tilted slightly to express his mild confusion.

Annabeth shuddered. Besides, he gives me a bad feeling.

Percy's nod was grave.

Both demigods turned back to the monster in question. There was a spark in his eye, something excited, but managed to send shivers down their spines nonetheless."You help me?"

Annabeth slowly shook her head. "I don't think we can."

The excitement died in his eyes, which widened, and turned into something much more desperate. "No! Nononono! You help! Please! Don't leave! Nonononono-"

Percy backed away as the monster weakly grabbed the bars, tears welling up in his eyes. Blue flickered off his fingertips, sparks dying quickly while a light halo of blue enveloped his figure. Steam wisped off his form as the cold air came in contact with him.

Percy's eyes widened at the power display and he quickly backs up. "I mean, uh, it would suck for us to break you out just for you to get captured again- there's kinda a whole war going on-"

Annabeth lay a hand on his shoulder. She put her mouth to his ear, whispering, "Nothing we say will justify us leaving him here, in his eyes. Besides, I don't think he's listening to you."

Quickly, she led him out of the chamber, guilt clawing her heart all while relief filled in the gap the dread had previously occupied. The blue glow increased and the sound of fire, flames built behind them. The daughter of wisdom didn't dare look back.

Percy had no such reservations.

What he saw chilled him to the bone.

The monster was coated in a blue inferno. His feral eyes watched the duo's every move in anguish as they moved closer to the exit. His mouth still moved with the unheard pleas. The runes surrounding his cage were glowing a faint white light when a small stream of flame approached, snuffing it out.

Rin screamed.

The sound was of raw anguish, undulated desperation. It contained a whirlwind of emotions, all tangled up in indecipherable knots. Percy's breath hitched when a very clear meaning rang out to him- loneliness.

(Loneliness was something Percy lived with his whole life. Before he turned joined Camp Half-Blood, any friends he met never stuck around. It was a combination of uncool, dumb, and how he was a "troublemaker" that drove away any possible friends.

Add in the fact strange stuff always happened to him, Percy tended to be alienated quickly at every new school he moved to.)

He didn't really have time to decipher much past that, since a split second later the blue fire surrounding him exploded into a tall column of cerulean flames that instantly blinded Percy.

Annabeth tugged at his hand. Percy started moving forward again, hadn't even realising he stopped. His eyes were squeezed shut, and the after image still painted a vivid image into his retna.

The duo left, the exit being almost identical as the entrance save for the last echo of the monster:

"WATASHI O OITE IKANAIDE!"

And a more broken whisper following that:

"Onegaishimasu..."

"Nidoto nai-"

Then they were gone.

AN:

Any use of the japanese language is from google translate.

Translations here:

Watashi wa anata ga koko ni iru koto o shitte imasu. Watashi o yashinau tame ni koko ni iru nonara, isoide is (supposed to be) I know you are here. If you are here to feed me, just get it over with.

Soretomo, anata wa koko de mokku suru nodesu ka? is (supposed to be) Or are you here to mock?

Jigoku is (supposed to be) hell

Yami no musuko is(supposed to be) Son of Darkness

WATASHI O OITE IKANAIDE is (supposed to be) Don't leave me

Onegaishimasu is(supposed to be) please.

Nidoto nai is (supposed to be) not again.

I say is supposed to be, because google translate isn't always the most accurate, but I took whatever was the closest to the phrase I wanted.

Anyway. This is a story that can definitely be expanded upon. However, I most likely will not, but if anyone wants to use this idea to form a plot just PM me and include me in a disclaimer somewhere.