Disclaimer: Characters owned by J K Rowling, obviously. The Mirror, imagined/owned by myself.

Summary: For everything in this universe, there is an opposite. Yin and Yang, Fire and Water, Light and Dark. So, for the Mirror of Erised, that shows you the deepest and most desperate desires of your heart, surely there must be an opposite? Beware, for when you look into the Mirror of Cosmaruri, you will see the darkest, most terrible nightmares – you will see whatever you fear the most.

The Mirror of Cosmaruri

Dementophobia

It was a blissfully ordinary winter's day in mid-December, and the sun was rising slowly over Hogwarts School of Witchcraft and Wizardry. The rough grey stones were blanketed in thick white snow that sparkled like a million diamonds, giving the school the appearance of a castle straight out of a fairy tale. Softly falling flakes whirled around in dizzying spirals, all dancing their own celebrative dance. Candle light spilled out of the hundreds of windows, in fat, golden and rose-pink smudges. It looked almost magical.

Muffled sounds of laughter and shrieks of delight echoed through the many corridors, the sounds of joy and children being children breathing life into the building.

It was the last day of term, and students were hurrying to the Great Hall for their last breakfast together, before most of them would return home for the Christmas Holidays. Inside, the enchanted ceiling sent snow falling, and dissolving, over the heads of the students, all chatting excitedly. One little group of students, however, seemed to be making (and causing) most of the uproar single-handedly. This in itself was nothing new – students were so used to the Marauders frequent cries of "food fight!" and random attempts to jinx passers-by (mostly Snape), that there was a permanent circle of empty seats surrounding the four boys. It had also become the fashion to wear Bubble Head charms and Protego shields around oneself while dining – just in case.

Today was no exception. Sirius was standing atop the Gryffindor table, arms spread wide, and head flung back, trying to eat the enchanted snow. James was howling with laughter, and standing on the bench, throwing bits of food at Sirius' open mouth – an irresistible challenge. Peter was clapping enthusiastically whilst hiding under his seat – he had once again woken up last, and would therefore be subject to "Snivellus Penance". You see, the Marauders had decided to be that bit more mature after That Incident, and Prefect Remus yelling at them to "treat others how you would like to be treated!" So, taking this quite literally, they were eerily nice to Snape for about a week, before he snapped one Thursday afternoon and burst into tears when Sirius offered to lend him a quill. Growing tired of a terrified Snape, and Sirius' random bursts of evil laughter, Remus devised a plan. For every jinx, hex and random prank flung in Snape's direction, one of the four of them must be prepared to be jinxed, hexed or pranked in exactly the same way. And today, it would be Peter.

Fortunately for the cowering rat animagus, Snape seemed to be avoiding the Great Hall, almost as if- "You don't think he's avoiding us, do you Moony?" whined Sirius as he plonked himself down next to the werewolf, and landed his elbow in the butter. Remus, laying his book aside, and swiftly moving the jam out of reach of Sirius' other flailing limb, raised an eyebrow. "Why on earth would Snape be avoiding you? Its not like you've ever, I don't know, turned his clothes invisible, or charmed his hair pink, or turned his pumpkin juice into POISONOUS ADDERS, is it?" Sirius frowned, evidently giving the question some serious thought, before he gave in and grinned.

"I see your point. But what'm I s'posed to do without darling Snivellus here to torment?!" Hiding his laughter, Remus turned to face his friend properly. ""Speak properly, Sirius. And firstly, "darling Snivellus?" I wouldn't let James hear that if I were you. Secondly, what happened to snow-eating, or whatever it was you were trying to do just now?" Huffing slightly at the light teasing, Sirius rearranged his face into a rather adorable pout. "Can't reach the snow. And James kept stuffing baked beans up my nose." Remus choked on his juice and grinned across the table at James, who stopped pigging out on the bacon long enough to give Remus a cheeky wink in return. Sirius caught the look and scowled. "It's not fair Moony! Padfoot WANTS the SNOWFLAKES!" Remus, sensing a Black Tantrum coming on, looked thoughtful. Then his resolve crumbled and he smiled helplessly. "The things I do for you, Padfoot." He mumbled under his breath, before pointing his wand at the magical sky.

"Finite Incantatem!"

Immediately the shield dissolving the snow evaporated, causing icy flakes to rain down on the students of Hogwarts. They remained blissfully aware of the fact, however, until James leapt up and summoned a fistful of flakes with a war cry of "SNOWBALL FIGHT!" The snow ball promptly met with the face of one Severus Snape, who had unwisely decided to enter the room at that exact moment. There were three long seconds of silence, during which Remus calmly packed up his books, Sirius took one last swig of pumpkin juice, and Peter tried to decide whether it was worth running for it, or if he should just accept his fate. His mind made up, he leapt to his feet, and ran. He had got no further that a few steps, when he was quickly buried under three simultaneously thrown snowballs. Apparently that was all that was needed to ignite a full scale revolt at Hogwarts. Students leapt up, Houses uniting to form armies, all immersing themselves in a 1000 person snowball fight. The teachers tried, and failed, to stop the mayhem, but Dumbledore just wasn't helping. With a cry of "If you can't beat them…" He had launched himself into a full scale snow-war with none other than McGonagall herself. By the time order had been restored, and the ceiling charms replenished, and people were beginning to look for the perpetrators of the chaos – it was discovered that the Marauders had already quickly and quietly disappeared.

If anyone had cared to look, they would have found them hurtling along the third floor corridor, chasing after what looked suspiciously like a fat grey rat. Sirius was running full pelt, and James was staggering along, weak with laughter. Remus loped alongside them lazily – he could've beaten them all without even breaking into a sweat, but the thrill is in the chase. Peter tumbled headlong down a flight of stairs, and dived into a suit of armor. Sirius gave a crow of triumph, and whipped out his wand, still running. All seemed to be lost for poor Peter, when quite by chance, Sirius tripped, sending his Summoning Jinx hurtling through the stair below.

Later, he would look back, trying to find someone, anyone, to blame for the events that followed. He came up with many answers – himself, for using a summoning charm, James for shoving baked beans up his nose, Remus for un-charming the ceiling, Peter for running, Padfoot for chasing. But when he thought about it… When he really thought about it, there had to be only one logical explanation. It was fate.

You see, quite by chance, the step the Sirius accidentally summoned had been cursed, long, long ago, and the sudden burst of Sirius' magic splintered the stone in a burst of white fire, freezing flames and waves of Dark Magic, engulfing Sirius whole, and sending him plummeting into the inky blackness beneath his suddenly unsupported feet.

He was falling, through the darkness, his screams echoing around the chasm, but nobody heard. Just as the shock of the fall began to fade, and surprise gave way to the panicky feeling that he would never stop falling, his body met with an unforgivably hard stone floor, his ribs cracking with the impact. He lay there, winded for a moment or two, his mind whirling. Where the hell am I? What the hell happened? Where is everyone? He sat up slowly, biting back a cry as his ribs gave a sharp stab of protest and he was forced to lie back down.

Shivering he blinked away tears of panic, and called out shakily. "James? Peter?" Gritting his teeth, he cast a pain numbing charm and scrambled unsteadily to his feet. Beads of cold sweat rolled down the back of his neck and he blinked, bright white spots fizzing in front of him, blurring his vision. Tentatively he called out again. "R…Rem? Remmie? Remus! REMUS! MOONY!" He staggered forwards, and fell to the ground again. He spat, tasting blood and grasped his ankle. "Yup." he mumbled, spitting again, a tooth hitting the uneven stone floor with an almost melodic tinkle. "Definitely broken." He shivered again, and pulled his robes tighter around him.

He drew an Exploding Snap card from his pocket, and transfigured it into a cloak. Keeping his wand firmly grasped in a shaking hand, he crawled forwards, using his free hand and an elbow to drag himself forwards. Casting a swift Lumos, he looked around and couldn't help the gasp that escaped him. The blue-gold light bursting from the tip of his wand lit up the chamber, letting him see the intricately carved walls, the high, vaulted ceiling that seemed to go on forever, and the- Oh Merlin. Oh, oh Merlin. Is that-?

Sirius felt bile rise in his throat as he saw. A large, rectangular object, the size of a wardrobe, covered in a deep grey dust sheet. And hanging in front of it, by a school tie- Sirius turned away, retching. He stood up, ignoring the stabbing pains in his ankle. "Relashio." He whispered, and the body fell, crumpling to the floor. Sirius knelt down next to the boy, and brushed back his hair. The Slytherins face was distorted in a wretched grimace of death, his jaw slack. His face was covered in old, dried blood, and what would once have been his eyes- Were now just empty sockets, bloodstained and leering. Sirius choked back a sob as he saw the boys hands, frozen into claws, his fingers stained. The boy had clawed out his own eyes.

His body smelt like decay, but the dusty room had done a good job of preserving the corpse. Sirius gulped anxiously, wondering why anyone would make their way all the way to this creepy room, just to kill themselves. And like this? Why claw out his eyes? Where was his wand? Sirius blinked sweat out of his eyes and looked around, the Lumos sending eerie shadows spilling out all around him. He eventually found the boys wand, broken and gnawed on by rats, discarded in a corner. He carefully picked up the two pieces and placed them in his pocket, his breathing shallow and unsteady. He spun around, his breathing gradually getting faster, his mind buzzing, his heart racing. What if he didn't come here? What if he fell? And couldn't escape-

Sirius shook his head, refusing to even entertain the notion that he would end up the same way as the poor Slytherin. He scrabbled around on the floor, until he found a loose chip of flint. Once transfigured, it made a marvelous pick axe. Raising it above his head, he brought it smashing down into the slate, buckling it, shattering it, revealing the dirt beneath. He couldn't stop the tears as he kept digging, digging and digging. Once he deemed it big enough, he half carried half dragged the corpse to the attempted grave and failing the ability to lay him down gently, he shoved him in, and rolled him over. He picked up the tie, and bound it round his empty eyes, whispering apologies as his tears fell. He crossed the unknown student's hands on his chest, and swiftly repaired the floor tiles. Then, with a small blade from his pocket, he carved into the stones: "Here Lies a Slytherin. A Student of Hogwarts. A Wizard."

Sighing, he staggered back, the blade falling with a clatter to the floor. He registered it dimly, and fell backwards, his legs no longer working. His back met with a hard surface, and he slid down, dragging the dustsheet with him. A few screams and moments of blind panic later, and the dustsheet was lying, blazing at his feet, his heart beating hard enough to burst through his skin. Gasping, he tipped his head back, leaning on whatever was behind him. He placed a hand flat on his chest, mumbling as he did so. "Easy there, Sirius. Just an old sheet. Its okay, just a sheet. A dustsheet. Covering-" He froze as he felt the cold seeping out of whatever he was resting against. He closed his eyes and took a deep breath, before slowly turning his head to the side, looking round, further, further-

He let out a scream loud enough to wake the dead, and threw himself backwards away from the eyes. Grey eyes, wild and terrifying, the echo of his fathers. His own. It was a mirror. He knelt up, and placed a hand flat on the mirror, staring at himself. He looked almost deranged. His hair was mussed, and there was blood dripping out of his mouth and nose. He gulped and then something swinging in his peripheral vision caught his eye. Slowly, slowly, he looked up.

The corpse looked back. There, above his kneeling reflection was a body, hanging by a gold and red tie, black hair matted. He was breathing faster, his head spinning. He knew, even before it span round, what he would see. There. His own face, distorted, his eye sockets empty and bleeding as he twitched and choked in the throes of death.

This time he couldn't even scream, just scrabbled backwards, not even standing up, until he hit the opposite wall, his mind clouded with terror. How was he there? How was he hanging from the ceiling, and sitting here against cold stone? He looked up slowly, turning his grey eyes to the body-

There was no body. He tipped his head back, tears of frustration bubbling from underneath tightly closed eyelids. "C'mon, Sirius, c'mon! It's just a mirror, just a stupid mirror…" He dragged himself upright and walked shakily back towards the ornately framed mirror that glowed eerily in the wand-light. He stopped a few feet away and closed his eyes tightly. He'd just walked over the grave of the Slytherin. "Sorry." He whispered, gulping, and risking a peek at the mirror. His own terrified reflection stared back. Sirius slowly raised a hand and waved, and the mirror copy did too. He let out a gasping sigh of relief, and turned- wait.

He turned back to the mirror, and walked forwards. That was him alright. But the Mirror Sirius' hair was immaculate, tied back in a ribbon like Lucius Malfoy's. Sirius frowned and raised his free hand to the back of his head. He let out a very unmanly shriek as he tore the ribbon away from his head, and flung it to the ground. It was his school tie, which had been draped loosely around his shoulders. Shaking, Sirius looked back at Mirror Sirius. The copy sniffed disdainfully, before his face broke into an eerie grin. Sirius watched with morbid fascination as his pristine reflection seemed to become a younger, better looking version of his father. It was still Sirius, with Sirius' bad posture and somewhat vampiric taste in clothing. But… His eyes were cold and hard, and the life that seemed to sparkle in them completely gone. It was a bit like looking at a dead copy of himself really, and Sirius would have been convinced that this was indeed the case if it wasn't for the cold smirk of the lips, and the haughty lift of the jaw, as though dismissing Sirius entirely. And there- there on Mirror Sirius' hand. His father's ring. And his father's cane. In his father's study. Paintings of mudbloods burning adorned the walls, and there- Sirius gagged and leapt back. Under Sirius' dragon skin boot-clad feet, a wolf skin rug. But not any wolf skin rug, a werewolf skin rug. And not just any werewolf skin rug, for that shade of amber, those tawny markings… That was Remus! He had morphed into his father and turned Remus, his own, darling Remus into a rug.

Sirius fell to his knees, his hands clutching desperately at his hair. "I didn't, I wouldn't!" But there it was, in full Technicolor. He watched as the image changed again, him, dueling James. Him plunging a dagger deep into his best friends chest, and- "Oh, oh no, no, no!" moaned Sirius, as Mirror Sirius ate James' heart, and laughed. "Oh God…" He whispered, and retched suddenly as he tasted blood in his mouth. It took a few frantic seconds of gagging and clawing at his bloody face before he remembered his broken nose. He sat heavily, sobbing, his nose running. "Stop it…" he whispered, pleading with the Mirror that seemed to know, seemed to know exactly what he feared. Mirror Sirius was standing there, torturing people, standing amongst the Slytherins, and he was the most evil of them all. More images, faster and faster. Regulus, burning alive at his own hand, his mother telling him she was So Proud, James screaming, hatred, so much hatred, and Remus…

Again and again, Sirius watched as his crazed Mirror-self killed his best friends, the people he loved, again and again and again.

He was clawing at his face, moaning in pain as he watched himself be consumed by the Black Insanity that ate his father. It ate his mother, and his little brother, and now, it had engulfed him too.

One final image of himself, silver gun with silver bullets twirling in his hands, and then it was gone, in a whirl of black fire. Sirius was breathing heavily, his eyes shut, his head bowed. Wearily he looked up, and flinched. His mirror self was laughing again and he could hear it, high and cold, insane.

"Stop laughing," Sirius whispered. "Please, please stop laughing." But the laughter wasn't stopping; it was getting louder, louder, insane and evil. His hands were held tightly over his ears, and he screamed at the pain of the sound, his own yells lost in the madness. He felt his eardrums shatter, and leapt to his feet, only to fall in a wave of dizziness and pain. He searched the floor blindly as blood ran into his eyes, until he found what he was looking for. He stood, his Gryffindor strength making one last stand against it all.

Mirror Sirius laughed as Sirius turned and swung the pickaxe with all his remaining strength. The metal hit Mirror Sirius hard on the shoulder – but it sent the real Sirius spinning backwards over the stones, his shoulder ripped open and bleeding profusely. He gaped at the un-damaged glass, ignoring the laughter that was causing his sanity to bleed out through his ears. His gaze fell to the grave of the Slytherin boy, and finally, finally Sirius knew how he died.

If he wanted to kill Mirror Sirius, he'd have to kill himself, because Mirror Sirius was him.

Future him.

Sirius let out a dry sob and cried out in pain once more, as he realized that with that last fall, one of his broken ribs had pierced the skin. He looked down at himself, bleeding, dying, and let out a choked whimper. "Oh, Merlin help me." He looked once more to the mirror, and that was his undoing.

Out from the mirror there seemed to pour an endless torrent of nightmares. Black and snarling, reaching out for him with fingers of fire, and ice, that froze his heart and glazed his eyes. Creatures that stole his breath and ate his soul. He could feel himself dying, lying there on the cold stone as the evil tore away his strength, his heart, his resolve.

His mind felt like it was being crushed, he couldn't see, couldn't breathe, couldn't think-"Sirius!"

Suddenly the world went quiet.

Sirius didn't move; just lay there, eyes closed. He could hear it again, James' voice, calling his name. But it couldn't be James, because James was dead, Sirius killed him, Remus too- "Sirius! Answer the goddamn mirror! Where are you? Sirius?! SIRIUS!" He staggered to his feet, not looking at the mirror, his eyes screwed shut. He pointed his wand to the ceiling and whispered, "Bombada". Somewhere, he could hear an explosion, shrieks of surprise. James was yelling something, but it was muffled, distorted. He swayed slightly, and pressed a hand to the still bleeding wound in his shoulder. He could hear people, calling his name, as though from miles and miles away.

He could hear Remus.

The werewolf sounded near hysteria, and Sirius couldn't help but smile uselessly at the sound of his voice. "I'm coming, Remmie. I'm coming." He threw his head back and with a flourish of his wand, and a sharp cry of "Ascendio!", he was hurtling towards the ceiling, his mind going blank as he spun upwards, out of the chamber, and smacked back-first straight into the ceiling above the third floor corridor staircase, and tumbled to the ground, the once gaping chasm silenced once more.

He felt himself being rolled over, and caught a glimpse of tears in Remus' eyes, yellow gold with fear, before he finally, finally allowed himself to fall into unconsciousness.

Author's Note:

In case you didn't quite figure – Dementophobia is a fear of insanity.

If you have any ideas about which characters you'd like me to feature, or what their phobias should be, review, and let me know m'kay?