Matou Shinji and the Philosopher's Stone

A Harry Potter / Fate Stay Night Story

Disclaimer: Though I wish it were otherwise, I do not own or in any way, shape or form hold a legal or moral claim to elements of either the Nasuverse, the Potterverse, or other works I may reference in the course of this story.

Summary: Ladies of Eternity, magi of the past hiding in the present, with ancient, nigh unfathomable crafts at their command. That is the destiny of a Witch in the Moonlit world, with the female child of a witch bearing the destiny of inheriting the blood and history of their line without any exceptions, upon which the mother will expire, her task done. But this is a story of a Witch's son – a boy tossed aside by destiny – a boy determined to become someone special, with blood, sweat, and wand. This is the story of Shinji Matou, and his newfound path in the Wizarding World.

Chapter 25: Belly of the Beast

"Don't touch the keys unless you have to!" Hillard barked out, as they came into the third chamber, with its many winged keys, wrought of all manner of metals and materials. "We don't know what charms might be on them."

"But there were no charms when—"

"—I went through this in my scenario!" George protested, his mind having had suspicions about the area since the group had subdued the disingenuously named Fluffy with an enchanted music box, with the Twins moving to scout the darkness below with their brooms.

Using Lumos to guide their way, they'd identified a chamber of what had looked like Devil's Snare, with some Venomous Tentacula mixed in. A dangerous combination, that. One plant – the one they had all had ample experience with by now would ensnare anything it touched, while the other would either riddle potential prey with spikes or inflict highly venomous bites.

Indeed, Professor McGonagall's husband, Elphinstone Urquart, had been killed by one such plant, leaving the Transfiguration Professor a widow.

Seeing this, the Twins had advised against jumping down and had scouted ahead, finding a brilliantly lit chamber full of what looked like small, jewel-bright birds, fluttering and tumbling all around the room, with a heavy wooden door on the other side. They'd frowned at this and pulled out the Marauder's Map, hoping that it would show them how many chambers there were to this dungeon – but these chambers were not on the map.

This was something of a disappointment, but then it made sense that rooms in Hogwarts would not be plotted if the Marauders had never discovered them – and these chambers were likely shielded against mapping attempts for obvious reasons.

Most importantly though, the chamber contained broomsticks enough for the others. Four of them, in fact – just enough – for the others.

That in itself was suspicious to the minds of the Twins, but there was really nothing for it. While their potions kits had each included a bezoar, the pranksters figured they would probably need those for Snape's challenge. So, they'd each grabbed a couple of brooms and brought them up to the group waiting up above.

Hillard had seemed surprised at their find, looking at the newly acquired brooms suspiciously, as if thinking they might be cursed with a Hurling Hex or some other manner of mischief.

Still…

"Did you say there was Venomous Tentacula down there?" he'd asked, to which the Twins had nodded. He'd taken a moment to weigh the pros and cons, but there wasn't much to weigh. "I see. Well – it's good to see the professors are taking the defense of the Stone seriously, but I don't think something of that level will stop Quirrell, do you?"

The entire group had shaken their heads.

"That's what I thought. We'll have to use the brooms then," the prefect concluded, shaking his head at the thought of what he was about to do. If someone had told him when he came to Hogwarts that he and a motley group of students would one day attempt to steal the Philosopher's Stone from under Dumbledore's nose, he'd have taken the person to St. Mungo's. But as the old wizarding saying went, "Reality was the strangest magic of all" – a saying not entirely unlike the muggle "Reality is stranger than fiction."

"Let's keep our wands out, just in case," Shinji had spoken up.

"Indeed. Be ready to levitate each other if necessary, or to help each other out of the Snare in case the brooms are jinxed," Hillard agreed. He was a prefect, damnit, not a trained burglar – even if the spell he'd used to open the door to the Cerberus (Alohomora), was known as the Thief's Friend. "Twins, go first since your brooms are known to be reliable."

The Twins had done so, with the others gingerly mounting the new brooms and following in their wake. Hillard, as an afterthought, had summoned the music box, so that in the worst case, if Quirrell came after them, he would have no sign that someone was already making an attempt on the Philosopher's Stone.

Quirrell would be bad enough to face with surprise on their side, if it came down to it. Without it, well…their only hope was that he'd focus on getting the Stone as opposed to ending whatever threat they posed.

Because if he focused on them instead…

Hillard shuddered. He knew the stories of You-Know-Who and his Death Eaters, stories that some parents still used to frighten bad children. He was the Wizarding World's bogeyman, against which the only talisman was the name of the Boy-Who-Lived.

The very boy who was mounting one of the new brooms, flanked by Matou and Sokaris. Though he knew they were competent, Hillard couldn't help but keep a careful watch on the trio who preceded him into the chambers below. Every legend had a kernel of truth, even in the Wizarding World, and he thought that the bravery of the Boy-Who-Lived in this said something about him – or at least, who he might become. And while he knew Matou had other motives to associating with Harry Potter besides friendship and loyalty, the young Ravenclaw wasn't as cold as he seemed to most people. He'd seen how kind Shinji could be in the moments he thought no one was looking – how Granger had cried herself to sleep in his arms, for example, or the little things that he and Sokaris did for each other.

Speaking of Sokaris…

Well, to be perfectly honest, he still had little idea about what the girl could do and just what her interest in the Stone was, but Harry and Shinji had both vouched for her, so that would have to be enough. That aside, she had been the one to let them know Dumbledore had left the castle and had displayed a surprising aptitude for potions, given that she and Matou had arrived at the rendezvous point unseen, their presence only revealed by a silent Homenum revelio.

There was no point in dwelling on that now though, as the group managed to successfully bypass the chamber of plants, proceeding slowly through a downward sloping stone passageway until they reached the threshold of the chamber where the broomsticks had been found.

"Merlin, those aren't birds – they're keys!" Hillard exclaimed after squinting a bit. "Let's not touch them unless we have to."

When the twins protested…

"There wasn't any Venomous Tentacula mixed with the Devil's Snare in your scenario either," Hillard pointed out, raising an eyebrow. "Which means that there's no guarantee the information in your scenarios was complete – or correct."

"I suppose he has a point, oh brother of mine," Fred groused, though he nodded.

"Just so."

"Perhaps it would be prudent for one member of the party to examine the door." Sokaris brushed an errant strand of hair from her face and eyed the door at the other end of the chamber gingerly. "While getting through will likely involve the flying keys in some way, we should make sure they are not a decoy."

"Good suggestion," Hillard agreed. He would go himself, but thought disillusionment might be picked up. This was likely Flitwick's set of defenses, and it wasn't unheard of for charms to react to other charms. It was quite possible that should they try using any high-level spells here, the keys would react violently. "Weasleys? You have a cloak between the two of you – are you up for it?"

While he knew Potter had one as well, the Twins were more experienced with this sort of thing.

"Sure. Leave it—"

"—to us—"

"—or to me, rather," George said cheerfully, dropping his broomstick, pulling on his invisibility cloak and disappearing from sight. The prankster took a deep breath and walked slowly across the room, keeping a wary eye on the keys hovering above, almost expecting to feel sharp metal ripping into him at any second, but nothing happened.

He reached the door untouched, wrapped his hand in a layer of the robe and pulled on the handle, only to find it locked. Even a quick Alohomora – which he almost expected to bring the wrath of the keys down on him - didn't work, though he hadn't really expected it to.

It would have been far too easy otherwise.

He headed back to the others and tugged off his cloak, looking for any reaction from the hovering keys, breathing a sigh of relief as he found none.

"No good. Door's locked, alright. Any bright ideas?" George asked, looking back to the other Stone Cutters, all of which were holding their…

Brooms.

"Wait. We got the broomsticks in this room, right, brother of mine?" George looked between the flying keys and the brooms in his comrades' hands.

"You're not saying—"

"—oh but I am, brother of mine—"

"—only I never figured—"

"—that Flitwick would like Quidditch this much?"

Shinji groaned as he looked between the brooms and the fluttering keys.

"…we have to catch the right key then?" he concluded. He liked the sensation of flying, he really did, but the boy from the east had quite felt comfortable on these. "Wouldn't it be easier for me to seal the movement of the one we want?"

"Maybe," Hillard allowed, "but we have to figure out which one is the right one."

And there were a teeming multitude of the keys, each darting and diving and moving too quickly for the eye to fully track. Even the Weasleys, with their Quidditch experience, were having trouble following what was what in the swarm.

"We're probably looking for a big, old-fashioned one," George noted, thinking back to what the lock had looked like. "Possibly silver, like the handle."

"Pity none of us are Seekers," Fred added, shaking his head. "Ah, right, Harrikins. You have a set of omnioculars, right?"

"Y-yes," Harry said, surprised one of the twins was asking him something. "You want me to see if I can find the key?"

"If you have one, then that's not a bad idea," Hillard said. "Good thinking, Weasleys. Harry, if you haven't used them before, omnioculars can slow down and replay action. Take them out, and I'll show you."

He moved over as Harry fished the golden contraption out of his Mokeskin pouch and spent a minute demonstrating how to record, replay, and such on them.

"Right useful things they are. Pity they never come with a manual," the prefect sighed, shaking his head. "Not that anyone would read one of those in the first place."

"Ah." Harry blinked, surprised at the device was capable of. He'd just assumed Sokaris had gotten him a fancy pair of binoculars, and hadn't found an occasion to use them before. "Thanks…Robert."

"The probability of success would be higher if we were already in the air," Sokaris suggested. "From the ground, it is difficult to determine where a key might be in a swarm, and we would have less time to seize a key even if you saw one."

Taking the suggestion, the group kicked off into the air, with the keys parting above them as they ascended, whirling about on rainbow feathers. Harry began scanning, weaving through the multitude for a minute or two when –

"I see it. A big silver key with bright blue wings!"

"Are you sure?" Hillard asked sharply. He had absolutely no desire to be scrabbling about on a wild goose chase. If he did, he'd have tried out for the Quidditch team.

To check, Harry pushed what looked like the rewind button on his omnioculars, hitting the freeze frame button the moment the key flashed into view.

"Yes," he said, flying over and passing the device to the prefect, who nodded, passing it to the next person, and the next, before it came back around to Harry. "But do we really want to try grabbing it?"

"…point," Hillard allowed, stroking his chin in thought. "I don't think Flitwick is the type to use anything Dark, but there are other spells that are used for defending things like treasure from those who don't have a right to it."

"Yeah. Bill mentioned a few—"

"—from his work as a cursebreaker for Gringotts," the Weasleys added. "Right nasty business—"

"—some of those even—"

"—eat a man from the inside out!"

Harry swallowed, the horrible vision of Daphne Greengrass being eaten away by darkness coming to his mind with utter clarity, flesh and bone dissolving into ash, her face contorted in fear as she was consumed by a curse.

His breathing grew ragged. No. If that was what waited, maybe it was better to give up now. He couldn't…what if…

"Harry Potter, steady yourself."

There was a hand on his shoulder, with Sokaris looking at the boy with something that might be sympathy.

"Sokaris, I…" Harry swallowed, his throat dry.

"Do you trust us, Harry Potter?"

Did he? And in what way? The Boy-Who-Lived knew the Weasleys were brave, that Hillard was experienced, that Shinji and Sokaris were more capable than other first years, but…

"Do not worry," the purple-haired girl continued, her eyes unexpectedly sharp. "I have no intention of sacrificing myself for you. I have my reasons for being here as well."

To most people, that would probably be less than reassuring. But to Harry – it meant that she wouldn't simply die on him. He'd seen enough death that the fear of it – the fear of others dying because of him – nearly paralyzed him. Would have paralyzed him, had the others not been with him.

He wasn't going to let them go alone, not if there was something he could do.

He nodded.

"Thanks," he said roughly.

Meanwhile, the Weasleys had flown over to Shinji, looking the boy over.

"That thing you did with the troll – do you think you could stop the key, if you see it?"

"Would sure be easier to grab something on the ground than in the air,"

"Indeed it would, brother of mine!"

Shinji's lips tightened as he looked at into the swarm of keys.

"I'll try it."

It was probably safer than casting a spell with a wand, since the ofuda would just go after its target, without the risk of hitting something in between.

He hoped.

So the Japanese boy sped down into the cloud of buzzing, swarming keys, each one moving about randomly, darting and diving so quickly that any one of them would be nearly impossible to catch. But then he didn't need to catch it – he just needed to catch sight of it.

There!

Swooping down towards the key, he pointed at it and cried out "Seal!"

A single ofuda shot from his sleeve, flying unerringly for the key and binding it—before burning to ashes, with two keys appearing where there had only been one.

'…shit.'

Knowing better than to try again, he flew back up to the group, reporting what had happened.

"Your charm burned up and two keys appeared?" Hillard repeated, blinking, not liking the sound of this. "What would have happened if one of us had touched it?"

"It sounds like the Gemino – "

"—and Flagrante charms—"

"—used for high security vaults at Gringotts –"

"Anything we touch will—

"—burn and multiply, but the copies—"

"—will be worthless."

"…that's great. But…how are we supposed to find the original?" Hillard groaned. "There are two of those keys now, and one of those will be useless."

"Mokeskin," Sokaris commented, holding up her silver-green pouch.

"Hm?"

"The interior of such a pouch is enchanted so that it can hold more than a normal pouch," the would-be alchemist pointed out. "Indeed – the size of the interior and exterior are incongruous, implying that if one were to grab something with the open mouth of the pouch, one would not actually be touching the object with the material."

The Stone Cutters shared a collective blink as they tried to process that.

"You mean…"

"…if we had Mokeskin pouches, then we could grab the keys safely?"

"Indeed, and due to the enchantment on it, once an object has been placed inside – even partially, none but the owner might remove it."

"That's—"

"—bloody brilliant."

"The issue remains that there are two keys at present," Hillard pointed out. "Unless there are two of us with—" He stopped cold as Harry sheepishly showed his. "That works then. Harry, Sokaris, since the two of you have pouches, you lead – we'll help herd the keys as best we can."

And so they did.

Harry, who had the Weasley Twins helping him, managed to seize hold of his key first, pinning it against the wall with the interior of the pouch. He used the pouch to grip what probably was the handle tightly as a burning smell came from inside.

Sokaris took slightly longer, as she didn't simply dive into the heart of the swarm, but seemed to circle above, eyes half-lidded in concentration – until at last she shot forward, capturing the key in a quick burst of speed.

Both landed quickly, heading to the door, with keys struggling futilely to escape from their Mokeskin pouches. Harry tried his key first, putting his key into the lock and turning it – only for it to crumble to dust.

A duplicate.

Sokaris tried immediately after, inserting her key into the heavy lock and turning it. This time it worked, with the key redoubling its struggles to escape now after the door opened.

But she wasn't about to let it escape, and forced the mouth of the pouch up over the keyshaft with the drawstrings.

"Come through with the brooms, and quickly," she said firmly. "Let's not leave our opponent a way through, if we can manage it."

The rest followed, flying into a chamber was so dark they couldn't see anything at all, the door closing behind them with a resounding thud. But, as Sokaris stepped into it, light flooded the room to reveal an astonishing sight.

They were standing on the edge of a huge chessboard, behind the black chessmen, which were all taller than they were and carved from what looked like black stone. Facing them, way across the chamber, were towering white pieces with no faces.

In the distance, behind the white pieces, they could see another door.

And in front of the black pieces, there was a pedestal, with a heavy book on it, a quill, and an ink-well alongside.

As Sokaris opened the book, motes of light swirled up from the old tome, forming seven words: "Would you like to play a game?"

"So we have to play our way across the room," Hillard commented, shaking his head. "Funny thing really. I'm a Ravenclaw but I never did like wizard's chess."

"Don't look at us—"

"—our brother Ron is the chess player—"

"—in the family," the twins chorused.

"Never had a chance to play," Harry said glumly.

"Shogi just isn't the same thing," Shinji added, looking at the board. "Is there another way across – can we fly, perhaps?"

Sokaris wrote down 'Do we need to play to get across?'

'Yes'the bookreplied in golden letters. 'The white king must be checkmated for the door to open.'

'Risk?'

'Abandon all hope.'

That…was not especially promising. Still, they'd come too far to give up now, and while Sokaris could play a good game of chess if necessary, she wanted to see if there were other options.

'What games are available?'

The listed options were: Falken's Maze, Gobstones, Exploding Snap, and Wizard's Chess.

None of them had ever heard of Falken's Maze, whatever that might be. Gobstones was right out, given that no one really wanted to deal with the prospect of giant stone balls that would spit something – perhaps acid or the like – at them if they were to lose a point. Exploding Snap – well, the reason they didn't want to deal with that game was obvious in the very name, as the cards it was played with…well, exploded without warning.

"I guess—"

"—Chess it is then," the Weasleys said uneasily. They had no great expectation that they would succeed in getting across…

'Specify number of players.'

…especially if they had to replace pieces on the board. They knew what happened during Wizard's Chess, after all – how a piece that was taken was eliminated by the attacking piece, often in a rather barbaric manner where the losing piece was smashed apart.

No one wanted to risk – at best – a concussion, and at worst, a stone sword through the gut.

Now, given probabilities of each piece surviving, it would seem logical to deploy the Stone Cutters as both rooks and the pawns immediately in front of and diagonal to them – in those positions, they would have a minimum of one in two chance of survival. Certainly, replacing any of the Knights would be a bad move – they only had a one in four chance of survival. The bishops did not generally fare better, with slightly over a one in three chance.

But though Sokaris' specialty was statistics and calculation, she also knew one other very crucial thing – how much losing even one Stone Cutter would demoralize the rest, and likely spell the end of this attempt on the Stone, so there was something she wanted to try.

Thus, she wrote '0' when prompted for the number of players, as the game simply began, faceless white pieces going up against and being smashed by black pieces and vice versa.

"What are you doing?" Harry asked, noting how the pieces were moving on their own. "What's going on?"

"Testing something," Sokaris answered, as she looked at the board, where the pace of the game was picking up. "The exact words were that the white king must be checkmated. The manner in which that needed to occur was not specified."

As if to prove her point, the white king took off his crown and tossed it on the chessboard, with the chessmen bowing and moving off the board, leaving the path to the door clear.

Surprised that that had worked, the group moved forwards, passing through the door and into the next passageway as the chessmen took their places again.

"…how did you know that would work?" Hillard asked, looking suspiciously at the younger girl who had outwitted the challenge so handily.

"I did not," Sokaris admitted readily. "However, in designing a challenge like this, it was likely that there was a workaround in place to allow testing, without putting the creator at risk. And if that workaround was not removed..."

"Clever," Hillard noted. It was certainly an impressive piece of logic, though her reasoning seemed more than a little too sophisticated for a first year. "And you thought that such a 'workaround' would be there?"

"It was better than the alternative," the purple-haired Ravenclaw replied. "Given the potential for unfavorable outcomes if we were to accept the challenge's rules, I concluded that the only winning move was not to play at all."

Hillard nodded. This was true enough, but…

"We are having a talk after this is all over," he said firmly. Frankly, with Sokaris having becoming so involved in the business of the Stone Cutters, this was something they should have done already, but more than ever, this adventure in the underground chambers was ringing alarm bells in his head.

For one, Sokaris didn't act like a first year. He hadn't really noticed before since he hadn't had the chance to interact with her extensively, but her stance, her language, her conclusions – even how she had prepared a bag of potions for them and arranged for house elves to wake up the Stone Cutters – those screamed of planning, experience, and a kind of calculation that wasn't the norm, at all.

"Certainly, Prefect Hillard." The girl nodded curtly, taking the lead as they moved into the room ahead of them, only to freeze at the sound of a low, terrifying laugh.

"No…"

"How philistine. To appear behind the curtain before the show starts. Have you not grown at all since that night, Eltnam?"

A voice spoke in the darkness, echoing in the chamber, as an elegantly dressed man in purple and gold clothing descended from the chamber above.

He opened his eyes, revealing blood-red orbs that bled endlessly and smiled – revealing a mouth full of wickedly sharp teeth.

A monster in human form, radiating enough killing intent to freeze them where they stood.

And for the first time, the group heard Sialim Sokaris scream.