Lily's first year, Rose's third year. (yes I am aware that that is redundant what with those being the same year, but some people do not know these things off the top of their head. some people including me.)
Lily/OC, Rose/Scorpius. The girls were pretty much set in stone by the prompt, and considering that nearly half the known characters are related to them...
... I feel like I should finish that sentence, for some reason. Oh well.
Oliver Cannon tried not to fidget nervously. Not because he didn't want to appear nervous (though that was the case) but because he was dressed as a character that didn't show much emotion. Halloween was his favorite holiday, as it provided a perfect excuse to go around acting like whichever fictional character he was obsessing over that year.
The reason he was nervous, by the way, was twofold. First, he was waiting in the Great Hall for what he was pretty sure was supposed to be a date. He liked Lily, of course, but at eleven years old, he wasn't too sure about the whole romance thing.
And second, Scorpius Malfoy was only a few feet away from him, apparently doing the same thing. Oliver hadn't been aware of the magical world very long, but he had heard enough to know that the Malfoy family were infamous blood purists. He didn't understand what was so pure about their blood as opposed to his own, it carried oxygen just the same... But he didn't think Scorpius would care.
After a few minutes, the tension was broken. "All right, Cannon, what are you doing?"
Scorpius frowned. "Waiting for anything in particular? You're not watching me, are you?"
Why, Oliver thought, would I be watching you? But that would be out of character. "I'm not watching you."
Scorpius's frown deepened. "So this isn't another one of her crazy tests?"
"I don't think so. Who's testing you?"
"... Forget it."
"All right, what are you doing?"
"You already-" Oliver started to point out that he had answered this question just a minute ago, but Scorpius was apparently not looking for an answer.
"I know you're weird all the time, but normally you're not weird in this particular manner. Why?"
Oliver sighed. "It's called role-playing. I am playing a role. This is Sig. You've never heard of him and probably never will, but this is how he acts, except for the part where I explain what I'm doing because apparently it's completely impossible to tell..." As he reached the end of the sentence he spoke faster and faster until he became completely incomprehensible in his rather misplaced rage. "Argh... I can't believe I broke character because of you."
Scorpius's expression relaxed a bit. "Can't believe you take your Halloween costume so seriously... That's really it?"
"Yeah. Just that. Nothing else."
For the next few minutes, Scorpius stood there being a Malfoy and Oliver stood there fuming, but nothing else happened.
"What did you think I was doing?" A little naggy voice in the back of Oliver's head reminded him that this was out of character, but he didn't care right now.
"It doesn't matter."
"Because, I'm pretty sure I've never spoken to you in my life..."
"It doesn't matter!"
"What with the whole blood purity thing that never made any sense to me..." Really? the naggy voice nagged at Oliver naggily. You're going to bring that up now?
Scorpius glared at Oliver. "I don't know what you've heard, but we're not like that anymore."
"... Not anymore?"
"Father was loathe to admit it, but the facts Mother showed him were impossible to deny. Purity of blood doesn't matter. It never did."
Oliver saw something white moving in the corner of his eye and whirled to face it, but it had already gone. "You see that?"
"I thought I saw... something. I'm not sure."
Scorpius took out his wand. "Homenum revelio..." He winced. "Should've known that wouldn't work. Too many people in the Great Hall..."
Oliver considered following after the figure, which he thought had gone up the stairs, but... "If Lily Potter gets here, tell her I'll be right back!"
"Um-?" But Oliver had already dashed up the stairs.
He didn't see anybody wearing white on the first floor, so he ran up the stairway to the second floor. As he reached the top, he was startled to find an arm thrust in front of his face, which he promptly ran into and fell to the ground. "OW!" He clutched his eye.
Oliver glanced up at the voice. "Lily? ... That was you?"
"Yeah, I'm spying on Malfoy for Rose."
"I see... so you ran off to tell her... what?" He stood up and blinked a few times. He didn't seem to be bleeding, and his vision didn't seem to be impaired. Thank natural selection for wizard toughness, I guess.
"Nice costume, by the way."
"Thanks..." Oliver knew a hint when it clotheslined him in the staircase, and examined Lily's costume. "You're dressed as Flonne," he said, compliments apparently being beyond his grasp at this point.
"There is no way you know who Flonne is," he said, flatly contradicting what he was seeing with his own eyes.
"You know that's not the case. I wanted to dress up as Etna, but-"
"There is no way you know who Etna is," he said, again flatly contradicting the blatantly obvious. But he couldn't help imagining Lily in Etna's demonically skimpy outfit. A drop of blood fell from his nose. "Damn it, I think you got me in the nose," he said, trying to stem the bleeding.
"Oh, sorry." Lily took out a Nosebleed Nougat and broke it in half. "I can never remember which end starts it and which end stops it..."
"The purple end stops it, I think. Though it oughtn't to do if it wasn't started by the orange end..."
She handed him the probably-stops-nosebleeds purple half. "It oughtn't to, but it does."
He chewed on the candy. "Don't get me wrong, it's a great costume, really authentic considering you can't possibly have any idea-"
"Oh, please. You think your little secret is, well, secret?"
He froze. "Huh. Could you perhaps be more specific?"
"From the Hogwarts front gate travel thirty-seven meters west along the fence, then travel straight out for eleven meters to play Muggle video games in the one spot on the grounds where the ambient magic isn't strong enough to make the device completely unworkable. That secret."
"Oh, that one."
"You realize this is a huge security flaw? I cannot believe you haven't told Headmistress McGonagall!"
"I have actually... And even if I hadn't, it's not like it's hard to notice a Muggle-born student using Muggle technology in the same spot all the time, when everyone believes it doesn't work in any of the spots any of the time. And from there, it's not too hard to realize that this might be a potential hole in the wards or some such thing. But she checked, all of the wards have their intended effect there, particularly the anti-Apparition one. Not sure why that one's more important but there you go."
"Oh. You think she'll move the Muggle Studies classroom?"
"Probably. Oh, and it's not just one spot. It's nearly a whole perimeter. I didn't think to check that, myself. So make that 'probably' an 'almost certainly, given that there's plenty of room'."
"That'll be nice, having Muggle Studies outside."
"Except in winter."
"So... What was it you were rushing off to tell Rose again?"
"Oh! I completely forgot I was doing that. I was heading off to tell her that Malfoy really isn't a blood purist."
"So... you were spying on him... to tell her... You know, this is an unnecessarily complex plan."
"I know, but as it involved my participation, I didn't bother pointing that out."
One status report later, the three of them were hading downstairs to the Great Hall; Rose to meet Scorpius, Lily and Oliver to... well, technically to meet each other, as they had agreed to meet in the Great Hall and neither of them was there.
"Okay, this is bugging me."
The girls turned to face Oliver. "What's bugging you?"
"You're Rose. You're Lily. Rose is dressed as Death. Only the flower of death is traditionally the lily, not the rose."
Rose raised an eyebrow. "That's what's bugging you?"
Lily smirked. "He has a point. I should be Death. You can be the angel nobody's heard of."
"I think not. As it happens, one person in this castle has heard of this angel, and that person is your date, not mine."
Oliver sighed. "I know, it's dumb, but it's a really blatant contradiction and it both- ow!" He slapped his neck. "I thought all the bees in the castle were exterminated..." he muttered to himself. "This isn't a bee." He looked at the dart he had pulled out of his neck. "What the crap?" He glanced into the empty classroom it appeared to have come from. It was, of course, empty. Profoundly so.
"Oliver, you coming?" Lily called back. She and Rose had gotten ahead of Oliver while he pondered a dart.
"Yeah, be right there." He looked into the classroom again. Definitely empty. "Probably just some stupid prank," he muttered, pocketing the dart just in case he was wrong.
The Halloween feast was winding down. Everyone had had a good time. The Slytherins weren't even as bad as Oliver had heard. Of course, there were a few jerks, but there were jerks in every House.
The four of them were returning to Gryffindor - of course Scorpius was a Slytherin, and Oliver was actually a Hufflepuff, but Lily and Rose were both Gryffindors, and it was only gentlemanly to escort their dates back to their House.
As they passed by that empty classroom, Oliver couldn't help but have another look. Still empty. No... not empty... There was something on the floor. He couldn't see it from here, he had to go in. He had to see it.
"...right, Oliver?" Lily turned to her date, only to not see him there. Because he wasn't there, due to being in a place that wasn't that place. "Damn it, he fell behind again. So easily distracted. Let me just go get him..."
"You probably shouldn't go off on your own at this time of night," Rose said. "I'm coming with you."
"Oh, don't be so paranoid. It'll only take a second."
Scorpius rolled his eyes. "This isn't a horror play. We don't need to go off alone and get killed. Let's all go, and be done with it."
"OlivHOLYDEMENTORSPIT" Scorpius quickly slammed the door he had just looked into.
"What? What is it?" Rose rushed over to Scorpius.
"N... Nothing," Scorpius said, remarkably composed considering his demeanor not half a second ago. "On a completely unrelated note, do you know where the headmistress is? Or perhaps the Defense teacher?"
"No idea. In their respective offices, I'd assume."
"Right, right. Could you do me a favor and retrieve one or both of them? And if you see any other teachers on the way there or back, bring them as well."
"Scorpius, what's in there?"
"I really don't think we ought to deal with this on our own..."
"Open the door, Scorpius!" The two scuffled in front of the door for a few seconds, but ultimately to no end, as the door opened without their intervention.
"Oliver! There you are! Lily was worried about you!"
"Oliver!" Scorpius stared, confused. "You're... completely normal in every way!"
"Why wouldn't I be, Scorpius? It isn't as though there were anything dangerous in this profoundly empty classroom."
Scorpius looked past Oliver into the classroom, which was, as claimed, profoundly empty. Not a trace of blood or dead bodies or demonic runes or sacrificial altars or any of the horrific imagery Scorpius had seen in there a minute ago. "That... is... true?"
"Yes. It is. Where is Lily?"
"I'm over here! And you! You had me worried! How could you just run off like that?"
"I apologize. I am far too easily distracted."
"You can say that again!"
The girls had been safely escorted back to their House, and Scorpius and Oliver were heading back down to their own Houses. All seemed well. But there was a little nagging voice in the back of Scorpius's mind, and he couldn't ignore it. Unfortunately, he also had no clue why it was nagging him.
"I believe here is where we must part ways, Scorpius."
"Yeah, it is..." What is it?
"I was wrong about you. You are not a horrible person at all."
"Thanks... I think..." What is it?
"Till next time."
"Yeah..." Scorpius turned to head off to Slytherin, and Oliver headed to Hufflepuff. "Hold up!"
Oliver turned around. "Yes, Scorpius?"
"What happened to your costume?"
Oliver looked directly into Scorpius's eyes. "What do you mean? I'm still wearing it."
Scorpius looked at Oliver again. He was wearing his costume, of course he was, he had no clue why he had thought otherwise... Still, Scorpius could swear he had seen Oliver in his normal clothes at some point this night. "Just my imagination..."
"Good night, Scorpius."
Rose had just gotten into bed when a small owl dropped a letter on her head. "Ow! Shoo, you dumb bird!" She watched the owl fly off into the night and opened the letter.
We need to talk. Real time. Might be life and death. -Scorpius
Enclosed with the letter was a small packet of Floo powder. "Seriously? This had better be as important as you claim..."
As she reached the common room, she saw something near the exit. She hesitated, but decided to follow it. As she reached the painting, she found it closed. Not that unusual, but when she tried to push it open, it wouldn't move. "That never happens..." She pushed harder, and suddenly the painting gave way, sending her sprawling into the hall. "Ow ow ow!"
"Will you be a little more careful?" The Fat Lady reproached her. "Also: another student out of bed?"
"Another...? Oh! Who left just now?"
"Lily Potter and that Oliver boy she likes."
"I definitely have to talk to Scorpius," she said, rushing back into the common room.
"And leave me hanging wide open, why don't you? Students these days..."
Rose met Scorpius outside that empty classroom.
"You didn't bring any teachers either?"
"I- I was standing outside the office and I got all nervous so I just threw down some Shriekbombs and ran!"
Scorpius gaped. "Shriekbombs? Forget it, at least it'll wake someone up."
"I don't see you bringing anyone!"
"Professor Slughorn was out of the office again and there's obviously not enough time to search the whole castle, I have the portraits looking for him but it will take forever."
"So... It's... down to the two of us."
"About that. The door won't open, Alohamora doesn't do anything-"
"Did you try Transfiguring the hinges?"
"I'm absolute rubbish at Transfiguration, actually-"
"Let me have a go." Rose whipped out her wand and pointed it at the bottom hinge. A few seconds passed, to no apparent effect.
"...Is it working?"
"Hush up and let me- OW!" Scorpius didn't have to ask what happened; it was plainly obvious. "It shocked me! The door shocked me!"
"I don't know any other spells to get past-"
"Then we'll open it like Muggles!" Rose started kicking the door by the knob, a slight look of madness in her eyes. Evidently the shock had pissed her off. Three kicks and the door crumpled inward, revealing a sight that made Rose disbelieve her eyes.
"I knew it!" Scorpius, on the other hand, had rather the opposite reaction. "I knew I saw something Dark in this room and now you can't hide it, you foul demoness!"
Blood was splattered throughout the room, not all of it fresh. Human corpses in various states of decay - though neither Rose nor Scorpius recognized any of them, and in any case there had been no mysterious disappearances lately. Bound and gagged in three corners of the room were Oliver, Lily, and a third student who Rose vaguely recognized as being a Ravenclaw, all still in their Halloween costumes and very much in distress.
In a circle at the room's center, various Dark runes were traced in blood and other filth (but mostly blood). And standing amidst the Dark runes, as Scorpius had so quickly deduced, was a demoness. There's no point in describing her appearance. Scorpius instantly recognized what he saw as a demoness, but the way she blurred as he moved his eyes made him suspect (correctly, as it happens) that she might have some sort of reflective illusion effect - a different appearance for anyone who looks at her.
"That's right, Scorpius... You're such a smart boy." The demoness grinned seductively. "You know, I need a smart boy, to help me. This ritual will extract all the powers of Hogwarts... But I can't handle that much power all on my own." She walked towards the two students, causing Rose to step back. "All you need to do... is give up the girl."
Scorpius considered this. "It's a tempting offer." The demoness's evil grin widened. "Or it would be, it if weren't a bald-faced lie!" The grin vanished like a... a thing that vanishes quickly. "You've got a Gryffindor, a Hufflepuff, a Ravenclaw, and a conspicuous empty spot. You just said I was a smart boy, but you clearly think I'm an idiot who can't complete a basic pattern! You really ought to be offering the power to Rose, but of course you know a Gryffindor would never accept a deal with a demon."
The demoness scowled, but quickly hid it with her increasingly transparent grin. "Of course... I can't fool you, can I? You saw this room for what it was, and then you saw through my disguise-"
"Because you forgot the costume! It's Halloween, you utter imbecile! Out of all holidays, you'd think a demon would understand Halloween! I could perform this ritual myself better than you've done." Keep stalling keep stalling keep stalling keep stalling. "Though, technically, I guess it isn't Halloween anymore. It's, what, one in the morning?"
"Yes, it is true that I missed the moment of greatest power... I am still debating whether to do the ritual as soon as possible, or delay for another year. It wouldn't be that long of a wait to me, but you humans move around so much, the chance of my being discovered in that time is vast."
"Definitely wait until next year," Scorpius suggested. "If you're going to do this kind of ritual, you want to do it right. An hour late's no better than a week late, you're wasting precious blood."
The demoness leaned in closer, inspecting Scorpius closely. "Are you sure you're not... stalling?"
"No! Not at all."
"Okay, yes, I am stalling! But it's also what I'd actually do if it were me."
She glared at him for a few seconds. "I see... It is genuine advice... But I'm afraid I disagree." And with that she lunged at Scorpius, but was blasted back by three simultaneous Stunning Spells. One from Rose, and two from the teachers that had finally arrived.
Rose and Scorpius wisely retreated to just outside the door to let the teachers deal with the situation.
A few hours later, the five of them were up in the hospital wing. Oliver was inspecting the Dark runes carved into his arms. They were carved pretty shallowly - it's a lot of cutting, and apparently it was important to the ritual that he not bleed out and die before the proper time. "Aside from the whole evil thing and the excruciating pain, these are actually pretty cool." Despite being pretty much glorified scratches, they couldn't just be magic'd away like any other minor injury, as they had been carved with Dark magic and as such required specific treatment. He had suggested just leaving them there, but...
"Out of the question. Aside from the lingering effects of the Dark magic, the very shapes themselves are... Keeping them is out of the question."
Lily was still scared out of her wits and was focusing largely on not flipping out. Due to a shortage of time, the demoness had only carved a few runes on one of her arms, but Lily expressed zero interest in keeping them. Oliver wanted to comfort her, but he was under strict orders not to leave his bed until his Dark runes were removed. He was going to suggest that his bed be moved over near hers, but they were bolted to the floor for some reason that he couldn't begin to fathom.
Rose and Scorpius, not actually being injured, were merely keeping their friends company. Somehow, despite having gone straight from the empty classroom up to the hospital wing with everyone else, Rose had managed to obtain the customary get-well candy. Scorpius had asked how she managed this impossible feat, but her only reply was "It is a secret. Forever." This only made him more curious.
The Ravenclaw seemed to be recovering just fine, despite having even more Dark runes carved into his body than Oliver. He hadn't spoken a word since being brought up, but according to Lily, he hardly ever spoke when there weren't any demonic rituals going on, so it was nothing to worry about.
In short, it was the scariest and most demonic Halloween ever, at least until the next year came around and... well, that deserves its own story, doesn't it?