Note-I have no knowledge on the Azkaban visitor system, and I do not own anything. I know Remus is slightly too angry to be IC, but I think that's fairly justified, don't you? Enjoy.
The prison was certainly dark, Remus Lupin thought. If it were not for the hunchbacked warden's slowly dimming Lumos, one would not be able to even make out the drawn, twisted faces behind the bars. He shivered, pretending to himself it was just the cold that made him do so, but really it was his lifelong fear of ending up here himself that made his bones shudder. He looked up; nothing with a sort of dry amusement that there was mould on the ceiling, and his shoes kept stepping in puddles on the stone floor. If one listened really hard, you could hear the faint slam of the North Sea hitting the stone walls of Azkaban. As they passed the inmates, the small Lumos charm cast a vague glow, and he was sure he could hear the inmates' desperate pleas for the light they had long longed for.
The warden wasn't speaking, and merely kept plodding along as the huge set of keys on a chain round his neck rattled furiously. Remus had tried striking up a conversation at the beginning of the "grand tour", but his guide's sullen answering grunts had promptly extinguished any pleasantries. The charm went out, sinking the room into the blackest darkness imaginable and the warden swore before casting the lost charm again. Remus rolled his eyes. He could have done better than a man who had spent his whole life watching prisoners, but his wand had to have been confiscated before he entered the cells, for fairly obvious reasons. The warden turned a corner into a corridor that seemed to stretch on into endless darkness, and Remus wondered how long it would be until the twisting Labyrinth of corridors petered out. Of course, that was the extraordinary design of the Azkaban. If you, by miraculous chance, escaped your cell, what chances were there of getting out the rest of the prison?
The warden, apparently registering Remus's hesitation, turned. He sneered with obvious malice, and Remus inwardly shivered.
"Are you too afraid to venture on, sir?" the guard said snidely. His voice was nasal, his matted and filthy blonde hair bypassing his shoulders and his hunch. "Not many wish to visit here, and you will find that many choose to turn back"
"No, no" Remus said agreeably, as if making an observation on the weather, and smiled nicely. "I do wish to continue, if it is not too much bother"
The warden snarled, apparently irritated at not being allowed to return to his skulking. Then he protruded a skeletal, arthritic finger, and slowly beckoned. And so the two men continued their journey in silence once again.
They presently arrived at what seemed like a large black hole, but was in actual fact a huge stone staircase that spiralled down and down, seemingly into the depths of hell and oblivion itself. Remus eyes the stairs with distaste, before the steward motioned for him to descend after him, and he did so. It was not difficult to see why so many went mad in this place. One could so easily loose track of time in such an eternal night.
After descending the stairs for what seemed like eternity, the pair reached a huge wooden door that stretched high up the wall. Remus could feel the buzz of millions of locking charms and spells, and the silver locks flashed menacingly, making him slightly dizzy. The warden noticed, and his lip curled in a way that was very similar to the Malfoy's trademark sneer. Then he produced a huge key from around his neck, and inserted it into the lock, muttering something which must have been a counter-spell as he did so. At once the whole place sprang into life. The whirs and clicks of a thousand hinges breaking apart were rusty, as if they had been deprived of their jobs for a long time, and the huge door groaned in agony as the bolts forced themselves into the oak. Remus almost gasped out loud as the scene unfurled. The warden glanced over, flashing his follower a bored look.
"Under Azkaban rules and regulations 189, all visitors to witness the unlocking of the Clandestine Cell must be issued with the Obliviate charm for reasons regarding Act 205 of the Wizengemot Disciplinary policy" he said in a completely deadpan voice. Remus nodded understandingly, and the warden flicked his wand. Remus felt his memories of the huge unlocking seeping away into nothingness, and he frowned. The warden smirked, and raised his wand to the mighty entrance to the cell.
"Alohamora" he said slowly, with a malicious grin, and the largest bolt in the middle of the door clicked open. "Can't say I'm jealous of your disposition, sir. In fact, I can't think why you are even here. He's a good catch to many"
Remus nodded patiently, the words of the guard blocked out by the sick feeling in his stomach and the rushing of his thoughts in his ears. Why was he even here? Was he completely mad? What inexplicable force had driven him here? But it was too late to turn back now as the warden gave the huge door a small push, and it swung open with a creak that sounded like a scream. Remus took a step forward, and it clanged shut behind him. He was well and truly trapped.
The Clandestine Cell was a hexagon shape, with walls that stretched up to, Remus guessed, where the staircase started, almost a mile above. The only light was from a spluttering enchanted candle that only betrayed a meagre flame. The room was damp, and freezing. It smelled of rot, and dirt, and madness. A scrap of blanket on the floor was an excuse for a bed, with a small, stinking pot for other functions. Remus wrinkled his nose. The place was disgraceful.
All the corners of the surprisingly small cell were dark, but in the one farthest away from him, Remus could just make out a hunched over silhouette, and a pair of watchful eyes regarding him, and rasping breaths. The room was silent.
The voice spoke, breathing heavily, as thick and coarse as sandpaper, and the cavernous orbs of blackness slowly blinked. Remus didn't respond.
"Remus? Is that you?"
"Yes" Remus replied blankly, not letting off a twitch. Now he was here, all his fear was gone, replaced by an unnatural calm. The shadow smiled widely, showing cracked teeth. He had the appearance of a wild thing. It was unnerving.
"Are they letting me go, Remus?"
"Of course not" Remus scoffed. The shadow hunched over again in clear disappointment. There was a loud, echoing sob, and then it reared its animal head again.
"You came for me? You are the first. Nobody has come before"
"No, I did not"
"Then why are you here?" the voice demanded. Its whole body seemed racked and stiff, and it could only speak in level whispers so as not to cry out in pain.
"You killed them" Remus muttered evenly.
"No I didn't. Listen, Remus, you have to believe me…"
"You killed them!" Remus shouted. The sentence reverberated off the stone walls before the darkness swallowed it up again. There was a short pause in which anything seemed possible. Then the shadow spoke again.
"Remus…please. I didn't kill anyone, I swear to you"
"Then why are they dead?" Remus spat, his voice slowly ascending into hysteria. "Why are James and Lily and Peter dead, Sirius, answer me that!"
"Rem…my old friend. You have to trust me. You're all I have left"
A loud sob ricocheted through the tower as the man called Sirius wept bitter tears. Remus was quiet.
"It's so dark in here" the man called Sirius continued. "S-so dark. Sometimes they leave you for days with no candle. It can drive a man mad"
"It's a just punishment for murderers like you"
"I didn't kill Lily and James!" Sirius yelled. "It was Pettigrew! It was Wormtail! He's the guilty one, not me! I would never-"
"You should be ashamed of yourself" Remus growled. "Blaming it on Peter, just like you always did at school" His pitch rose in mock imitation. "Please, McGonagall, I didn't charm those Slytherins just out of reach of the Squid, it was Peter, I swear"
"I never betrayed anyone" Sirius protested dully.
"Still pretending now?" Remus ridiculed. "Still telling yourself it was all for the greater good just so your precious master would kiss you goodnight at the end of the day?"
"I would never, ever work for Voldemort"
"Oh, yeah? And I don't change into a slavering beast every full moon" Remus muttered sarcastically. "They're dead, Black, and it's your entire fault. And their son, your godson. Little Harry Potter, living with muggles in Surrey. Oh, I bet that would make your master very happy"
"Harry…" Sirius whispered. "How is he? Is he ok?"
"Oh, yeah, he's just peachy! Apart from the fact that he'll grow up an orphan, not understanding who he is until he's twelve, he's bloody fantastic! How could you do that to a child, Black? I suppose it's in your blood"
"Shut up" Sirius rasped half-heartedly, but Remus continued regardless.
"Is that your excuse? Your family? Well, at least you'll be able to spend all your time with mummy and daddy in here!"
Sirius growled, shaking the chains that had him firmly attached to the wall. Then his breathing slowed.
"It was the full-moon last night, wasn't it? I could hear the screams from the security wards. So…I can't blame you for this anger, Moony"
"Don't you dare call me that, Black. Don't you dare call me by my nickname"
"I'm sorry, Remus" Sirius muttered. He'd lost every fight he'd been in recently, even the ones against himself. He'd lost the spirit in him, Remus noted. "But you have to understand that I am innocent. Please, Rem. You're my only friend left in the world"
Remus was trembling from head to foot.
"Yeah. You killed all my other ones" he sneered.
And to his complete and utter confusion, Sirius laughed.
"Remus John Lupin…" he muttered. "They've changed you, mate. I thought you were the reliable one who would never let down a friend in need"
"I tried not to, but you got to them first"
"They're my friends too, Remus"
"Were, Sirius. They were your friends. God, you bloody bastard…"
"I didn't kill them"
Remus wearily ran a hand over his face and smiled thinly at the convict.
"Please, Moony. Please. I didn't…Marauder's honour. Please believe me"
"No. I don't" Remus replied. "You killed three of the dearest friends I ever had. You are no Marauder, and I won't ever believe you"
Behind him, the door rattled open again, and the warden's grime-streaked face peered in warily through the gap.
"Time's up" he muttered, not taking his beady eyes off Sirius. Sirius roared, and shook at the shackles again. Remus stared in his friend's eyes, taking in the deep, rich darkness in them, and the terrible fear in his face. Then, he slowly turned, and left the room.
"Moony! Moony!" Sirius screamed in an agonised cry, and the relentless sound followed Remus all the way up the stairs as the solid door closed behind the friend he would never see again.