I don't own Harry Potter.

Please let me know what you think.

X

Sex Night.

Holly and the other Slytherin Third Year girls returned to their dormitory, while the girls from the upper years returned to their own dormitories. Their bodies were covered in thick sheens of sweat and dried, drying, and still wet cum. All of the girls were exhausted, and yet at the same time they felt more relaxed and more fired up than they had ever done before.

Something had changed with them.

The older girls ahead were openly chatting and giggling away at the amazing sex they'd had, comparing the different cocks and pussies they'd fucked or humped.

Holly and her friends were the same. More than once Holly had caught herself masturbating at the thought of more sex. Pansy was the same, and so was Lily, and Millicent.

Tracy and Holly enthusiastically exchanged notes on some of their own partners, while the others gossiped about how good their sex was, and how bad.

And for a girl who had been declared the Ice Queen for her manner, Daphne Greengrass had changed forever. To the world, she was seen as an Ice Queen, a cold and aloof girl who showed little emotion.

But not anymore.

Her blonde hair was mussed up. Her body was covered in dried cum and her pussy was still coated in still wet cum. And she was gossiping and giggling with the other girls. She was now an open slutty whore, and her friends were no different, and rather than feel shame, Holly was quite proud of being a slut.

As one, the girls went to the showers to wash off the night of hardcore sex. As they stepped into the shower cubicles and manipulated the runes according to their tastes, the showers turned on. As the water sprayed over their forms, the girls gently scrubbed themselves down thoroughly, washing their hair and then quickly wrapping their hair in towels. They knew they could have charmed themselves dry, but they had decided silently to have a talk about what happened.

The Slytherin girls loved to gossip. And contrary to what many in the school liked to think, in the dorms the girls were quite close together.

Holly sat on the edge of Daphne's bed, trying to keep her flushed face at being so close to her blonde dorm mate. "Well, I don't know about any of you, but I don't know if that was real or a dream. I feel like I've just passed through a strange dream, and I was awake the whole time."

"I know," Lily nodded.

"We've all had sex with numerous boys and girls," Tracy piped up with a dreamy grin as she clearly remembered the pleasure she had gone through. "Oh, it was so fun!"

"You horny skank, Tracy," Holly giggled, and exchanged amused looks with Daphne and Pansy, but they admitted they'd also had fun.

"Oh, you can talk, Hols," Daphne snorted. "How many times did you yourself suckle my tits?" She cupped her breasts for emphasis.

"Yeah, they're nice tits," Holly nodded, trying to make sure she wasn't blushing scarlet. "Never disrespect the tits."

Daphne rolled her eyes.

"But seriously, what the hell happened? What made us act like that?" Holly asked seriously. "I mean, we've been feeling horny all day, and not just us but the boys, too."

"Some kind of potion?" Tracy suggested.

Millicent shook her head. "No. It would fit, and there are potions that can make somebody horny, but I can't see it working like that."

"Some sort of Runic enchantment, perhaps?" Pansy offered.

"Yeah, but why? Why would somebody go to the trouble of doing all of this?" Lily looked around.

Holly sighed, and she had to blink her eyes rapidly to keep herself awake. "We can ask that tomorrow," she decided, demonstrating that while Pansy was technically in charge of the gang, she was the one who had true leadership qualities. "Right now, we're tired after the night we've had."

All of the girls nodded and murmured their agreement, but Pansy was curious. "Who are we going to ask, Professor Snape?"

"Him and the Slytherin Portraits," Holly smirked at their expressions of surprise. "Didn't you notice, the Slytherins in the portraits and tapestries which show the adventures of famous Slytherins of the past were also having sex? This has clearly been going on for centuries, perhaps since our House was founded."

"Salazar Slytherin's portrait is in the Common Room. We can ask it," Daphne quickly proved why she was one of the top students of their year, with Hermione Granger and Holly.

Holly nodded as she slipped off the towel and chucked it into the laundry basket close to their bathroom entrance.

"Exactly. We were too busy tonight," Holly smirked at their chuckles and blushes, "but tomorrow morning will be different. Right now, let's get to sleep."

"Y'know, Holly," Tracy commented as she donned her nightie, not bothering with hiding her spectacular body as she did. They had all gone beyond the realms of modesty after tonight. "Tomorrow is Saturday, and most students sleep in, so whoever set this up knew that was going to happen."

Holly nodded, although truthfully it hadn't occurred to her at all. But hearing that reasoning made everything click more in her mind. "Mm, good point. Now let's get some sleep."

Holly slipped into her bed, relishing the feel of the soft cotton against her skin. Thanks to their exhaustion, the girls got to sleep quickly but Holly remained awake for a little while; a holdover from her time living with the Dursleys, she would lay awake for a little longer and would only sleep when sure it was safe. But tonight as she fell asleep, Holly realised she was extremely tired after the night of fantastic sex from so many partners.

She had felt the euphoria, the rush of power in the aftermath of the night, and how the desire to have sex had virtually gone away, although she still felt the love of sex even now.

Holly would find out what happened tonight, but she knew one thing.

She wanted to have it again.

As she fell asleep, she heard the sound of muffled moans from some of the other girls. She knew they felt the same, they were masturbating.

X

The next morning, the Third Year Slytherin girls had a long lie-in before they decided to get up and out of bed. Groggily, although they felt refreshed and energised, they took off their night things - if they were wearing them, that was - and they went into the shower. Gently they scrubbed themselves clean and washed their hair before they used their wands to dry themselves.

Holly slipped on a pair of panties and pulled them over her groin before she put on her bra, and then a clean shirt and jumper. Today she elected to put on a pair of tights, and she pulled them all the way up her legs so they would highlight her long legs. After pulling up her short skirt, Holly sat down at a vanity table and pulled out her wand. Most witches preferred using cosmetic spells, and Holly was in between. She was still trying to master how to put on makeup, muggle style, but in Hogwarts, it was easier and simpler with a wand, but she still practiced.

Gently, mascara appeared on her eyelashes before she applied a pink eyeshadow and highlighted her cheeks before finishing off with pink lipgloss. Summoning her hoop earrings to her, she slotted them in place and gave herself a wink after looking at herself in the mirror.

There was a knock at the door before an older Slytherin girl stuck her head in. "You girls up? You need to come to the common room."

"Why?"

"You're going to get the sex night story."

X

Holly and the girls were not the only ones who were gossiping about the sex they'd had from sex night. The boys were too.

"I swear, Daphne Greengrass isn't as cold as we've been led to believe, guys," Theo Nott smirked.

"And not just her," Blaise was saying. "I wouldn't mind having another go with Potter. She's a right little slut."

"That she is. I always fancied her, you know," Malfoy commented.

"You do?" Crabbe asked in surprise. "I always thought you looked down at her for being poor and was jealous because she's a ward of the Black family?"

"That's a good point, Malfoy," Blaise pointed out.

"Maybe I do, but you guys can't deny she's hot," Malfoy saved himself.

At that point, the girls in their year appeared. Malfoy and the boys kept themselves quiet as they gazed at the beauties in front of them - even Millicent seemed to have lost some of those traits that made some view her as a female Crabbe and Goyle.

"So, what's the story?" Holly asked bluntly.

"Dunno, we were told to come down here, same as you," Nott replied, gazing appreciatively at the girl. Holly was one of the most prettier girls in their year, everyone knew that, and she looked even more gorgeous right now. Instead of being oblivious, Holly gently lifted her skirt and showed him her panties with a coy smile.

"Indeed you were," a smooth, rich cultured voice said. The Third Years jumped when they heard Salazar Slytherin's portrait speak. Holly had spoken to the portrait once or twice for advice about magical culture, but in truth, she'd planned to speak directly to the portrait and demand bluntly if the portrait knew about why they'd gotten so horny and rabid for sex last night.

Holly nodded, and she stepped forwards, the other third years letting her be their spokeswoman. "Were you responsible for what happened yesterday to us?"

Slytherin nodded. "Yes. When a new Slytherin walks into the common room and spends the night, they are added to the list of students. In their teens, their third year, a runic mark will appear in the skin and make them desperate for sex."

"Why third year? Some kids have sex a year younger?"

"Because at thirteen, your bodies are full of hormones and your magic has become strong. Long ago, times were desperate for the magical world. Our conclaves were always under constant attack from the muggles, and there were fears of persecution should schools be built in a desperate bid to ensure our way of life endured," Slytherin began to explain.

More than one Slytherin muttered about filthy muggles. Holly was one of them, although she did like muggle culture. But truthfully she didn't care about them.

Slytherin went on. Clearly, he had heard this all before and he'd learnt to ignore it. "In my youth, I was renowned for my skill and my cunning. I studied and developed parseltongue, and many other forms of ancient magic in order to survive. Thanks to my efforts I was able to save many of our people before meeting with the other founders, but that was not enough. In the past, I found a ritual that employed sex magic in order to boost my natural powers. And it helped. I became stronger and I would never have survived to become a part of the founding of this school if it wasn't for those rituals."

"And you wanted future Slytherins to gain the same strength," Daphne nodded.

"Precisely," Slytherin replied. "I never wanted my students, past or future going through what I had done in my youth, where those muggle animals slaughtered and endangered our kind. Every month, there are three sex nights. The ritual will begin with a runic mark appearing on your skin and then fading away, leaving you in a constant state of arousal the day before you come to the common room in the night. The first and second-year dorms are warded to stop them from hearing or seeing anything, but even if they do there is little that can be done."

Holly wasn't sure if she should like that part, but it explained a lot from her first two years. She had noticed several of the upper years being excited and happy. Now she knew why. She didn't like the thought of the runic mark, or the thought of being horny for an entire day, before having sex in the common room late at night.

And that gave her the courage to ask her next question. "Excuse me, Lord Slytherin," Holy waited for the eyes of the portrait to focus on her, "what would happen if two Slytherins had sex before the night on those particular days?"

Rather than be shocked or horrified although Holly had a feeling that the portrait had heard this question before, Slytherin instead chuckled. Her suspicions were confirmed. He had heard this before. "It makes no difference, my dear. Sex night is inevitable, but if that were to happen, then the two Slytherins would be utterly insatiable."

"I see," Holly nodded. But then she had another question. "What about the other Houses? Do they have a sex night?"

"No, I tried bringing up the merits of it with the others, but they didn't want to subject their students to anything like that. I don't see why, especially since Helga gave phenomenal handjobs," Slytherin replied.

X

To outside observers, the Slytherins who walked into the Great Hall en-masse were the same as ever. United against a school run by a senile old man who favoured a quarter of the population, the Slytherins were almost alone. However, Dumbledore's favouritism was clear to the Hufflepuffs and to the Ravenclaws as well, who more or less suffered from it.

With Neville Longbottom the Boy Who Lived at their helm while Dumbledore supported them, the Gryffindors were the ultimate bullies. What was worse was how Dumbledore punished the Slytherins for bullying when in fact it was simply self-defence. To the outside observer, the Slytherins were the same as ever, keeping to themselves mostly while they checked their plates and food for pranks and potions, a new tactic taught to them by Holly Potter.

But inwardly, the Third Year Slytherins knew much had changed for them, and as the year passed and sex night because a common occurrence, they began changing with it.