Disclaimer: I don't own Harry Potter. Most of the backgrounds of the characters are canon. Just a few details are from my head.
Hogwarts had been a school for the last thousand years, having been built for this purpose by the greatest witches and wizards ever. Not many of the students who graced her halls knew that the castle was sentient. She absorbed all the latent magic of her location and all the magic used by the students when not in class. She usually was content to merely watch the day-to-day goings on, but the feud between the houses of Gryffindor and Slytherin was unnecessary. She waited for her chance to change that, and at long last, the time had come.
Severus Snape and Regulus Black were on the seventh floor on their way to the Room of Requirement. Unbeknownst to them, they were being followed by two different pairs. James Potter and Sirius Black were using the Marauder's Map to track their two favorite targets. They were so single-minded about ranking the two Slytherins that they took no notice of the four prefects converging on their location. Lily Evans and Remus Lupin were following their fellow Gryffindors, certain they were up to no good. Lucius Malfoy and Narcissa Black were actually following Severus and Regulus to make sure that they made it safely to their destination.
When the eight students reached the location of the Room of Requirement, a door materialized and opened on its own accord. A wind vortex sucked all eight students inside, and no amount of struggling prevented their entrance. Once all four Gryffindors and all four Slytherins were inside, the door closed, and Hogwarts sealed the room until the eight inside could resolve their differences.
"Potter, what did you do?" Lily accused.
"If I did this, why would I trap us four Gryffindors in here with these snakes?" James countered.
"He has a point, Lily," Remus admitted.
Ignoring the Gryffindors for the moment, Lucius and Narcissa made sure their fellow Slytherins were all right.
"Sev, Regulus, are you all right?" Lucius asked.
"Lucius, what are you and Cissy doing here?" Regulus asked.
"We were following you two to make sure you weren't being targeted," Narcissa answered.
"I can't believe those jerks got us," Severus muttered angrily.
"I'm not entirely sure this is their doing," Lucius admitted, hugging the angry black haired boy.
Severus was confused. "Why would you say that?"
"Of all the times you've been targeted, how many times did the two troublemakers stay in the blast area?"
"None that I can think of," Severus replied, his anger diminishing. He looked over at the Gryffindors and noticed Lily. His anger completely vanished at the sight of his best friend. Seeing his brother in all but blood wasn't angry anymore, Lucius let the other Slytherin go. "Lily!"
The redhead looked over at the group of Slytherins, her verdant eyes alighting on her best friend. She crossed the room, meeting him in the middle between the two groups. "Sev!"
Lily pulled Severus into a brief hug, which made James jealous. "Let go of Lily, Snivellus!"
Lily whirled around. "I can hug whomever I want, Potter. For your information, Severus and I knew each other before we came to Hogwarts. We are friends; nothing more."
James's mouth dropped open. "I didn't know that!"
"There's a lot that you don't know, Potter!"
Suddenly, a piece of parchment floated down from the ceiling, and Remus grabbed it and read it out loud.
This is the Room of Requirement. You are stuck in this room until you get along with each other as the feud between Gryffindor and Slytherin is unnecessary. Please do not worry. Time will not pass while you are in this room. Get to know each other. You might be surprised.
"Get along with Slytherins?!" James and Sirius exclaimed in unison.
"We'll be in here forever," Remus muttered under his breath, knowing how stubborn the prankster duo could be.
"We could try to do what the note said," Lily suggested. "But either Remus and Lucius hold onto everyone's wands or we can try to have Hogwarts secure the wands to the ceiling."
The Slytherins passed their wands to their male prefect with no protest. Lily gave hers to Remus. The werewolf looked expectantly at his year mates and held his hand out, waiting none too patiently. "Either hand me your wands or they will be secured to the ceiling."
With a glare at the Slytherins, James and Sirius reluctantly handed Remus their wands. Remus put all three wands in the pocket where his wand was.
"Looks like Hogwarts wants us to sit here," Regulus pointed to eight chairs arranged in circle. Each chair had a name tag on the floor in front of it.
"I refuse to sit next to a Slytherin!" James exclaimed.
"Hogwarts took that into account, Potter," Lily retorted. "You sit between Black- Sirius, that is,- and," she grimaced, "me."
"And Sirius sits between me and James," Remus added.
The Slytherins watched as the four Gryffindor sixth-years sat down. Once the Gryffindors were seated, the Slytherins approached the circle of chairs. Severus and Lucius were first, followed closely by Regulus and Narcissa. Severus and Lucius were across from James and Sirius. Regulus was seated between Lily and Severus, while Narcissa was between Remus and Lucius.
James looked to his right at Lily and said, "You said there was a lot I don't know. Like what?"
"I live in the same neighborhood as Sev and spend my summers with him."
"I'm sorry, Lily. I won't be able to meet up with you this summer," Severus said softly.
Lily whirled to face her right and locked eyes with the sixth-year Slytherin. "Has it gotten worse?"
"The worst ever."
"Hold on!" Sirius interrupted. "There are people here not in the loop."
Severus sighed. "I'm a half-blood. My mother is-was a pureblood, a Prince by blood. She was disowned when she married my muggle father. When he found out our wizarding heritage, he turned abusive. Fueled by fear, alcohol, and unsteady employment, he tried to beat the magic out of me. Since we lived in a muggle neighborhood, we can't-couldn't use magic against him, even in self-defense. The weekend before school started he killed my mother."
Lily gasped, tears jumping to her eyes. "Oh, no! Where are you staying?"
"The police arrested Tobias, who was charged with murder, and Severus lives with me for now," Lucius added.
James and Sirius sat there in complete disbelief. Remus was also in shock, but was able to shake it off. "At least you are safe now. I also have a muggle parent, but it's my mum who's the muggle. My father saved her from a boggart, even though she didn't know it was a boggart. They won't tell me what form it took. I am fortunate that she was so understanding about us being wizards. She's so easy going, even when I was bitten-" Remus slapped a hand over his mouth. He hadn't meant for that to come out. Half of the circle (James, Sirius, Severus, and himself) knew his secret, and the other half was smart enough to infer it due to his slip-up. He hung his head, waiting for the inevitable verbal onslaught.
Narcissa, being the one sitting next to Remus, recoiled at the thought of sitting next to a werewolf. Lucius was about to comfort his girlfriend until he saw Severus lower his head. Lucius looked at Severus. "You knew?" The raven-haired sixth-year simply nodded. "How did you find out?"
"I can't say," came the soft reply.
Noticing the duo across from him were fidgeting, the blonde sixth-year glared at them. "Explain."
James and Sirius looked at each other, and Sirius nodded at James, who spoke. "Padfoot noticed that Sni-Snape was spying on Remus to try to figure out where he goes every month. He decided to tell him how to get past the Whomping Willow. When he told me, I realized that Snape could've been bitten or killed. I was relieved when I got there in time to prevent either of those outcomes, but he did see Remus transformed. The Headmaster forbade Snape from telling anyone about these events. It was all Sirius's fault. Neither Remus nor myself were involved in the plan. We just got caught in the aftermath."
Lucius narrowed his eyes, which caused Sirius to look away. He was barely able to contain his flinch. "Well, Snivellus deserved it!"
"How reckless can you be? You risked your friend's life for what? Revenge for some imagined slight?"
"There was more at risk than Remus's life! Prongs, Wormtail, and I would've been expelled too!" Sirius exclaimed. "In satisfying his curiosity, everything would've been exposed. It would've been a front page headline! Werewolves, Maps of Hogwarts, and Illegal Animagi- More on page five!"
James elbowed Sirius in his side. "Nice going, Padfoot. You just spilled our three biggest secrets."
Sirius slapped a hand over his mouth, but it slid down a second later as he realized it couldn't be taken back.
"Maps of Hogwarts?" Regulus inquired.
"Illegal Animagi?" Lily asked.
"We have some explaining to do," Remus commented. After giving a sigh, he added, "We made a map of Hogwarts including all the secret passages we could find. It also shows everyone in the castle, what they're doing, every moment of everyday."
James pulled out a thick folded bunch of parchment and held it out to Remus. "You'll have to do the honor, Moony."
Remus pulled out his wand and placed its tip to the parchment James held. "I solemnly swear that I am up to no good."
Everyone watched as, as if written by an invisible hand, words appeared on the parchment. It read:
Messrs Moony, Wormtail, Padfoot,
and Prongs are proud to
present The Marauder's Map
Lily and the three Slytherins sitting away from Remus got up to see the map better.
"Who are Moony, Wormtail, Padfoot, and Prongs?" Regulus inquired.
"You made this?" Lily asked.
"That's how you always know where I am!" Severus exclaimed.
"I'm Moony," Remus said.
"I'm Padfoot," Sirius continued.
"I'm Prongs, and Peter is Wormtail," James finished.
"Why did you choose those names?" Narcissa questioned.
"It goes back to what Sirius confessed. It goes with our Animagus forms and Remus's werewolf form," James answered.
"Can we see?" Lily asked.
James looked at Sirius, who shrugged his shoulders. James stood up and shifted into his stag form. However, Sirius remained sitting when he shifted into his dog form, which resulted in a big black dog sitting in the chair.
The duo of animals shifted back to human form, causing Regulus to stare at his brother in amazement. The staring unnerved Sirius, prompting him to ask, "Why are you staring at me?"
"Truthfully, I admire you, Sirius. You had the guts to do what I couldn't do. I don't believe in the pureblood propaganda, but I have to pretend I do for several reasons. In Slytherin, there are supporters for The Dark Lord. At home, I run the risk of being disowned and blasted off the tapestry in addition to losing access to the family fortune and the prestige of being the Heir to a Most Ancient and Noble House," Regulus admitted.
It was Sirius's turn to stare. "I never knew, Reg."
James narrowed his eyes slightly. "Who's The Dark Lord?"
Lucius answered, "The Dark Lord is a rising pureblood supremacist who wishes to rid the world of either those who oppose Him or those whom He believes don't deserve to use magic. He has gathered supporters from most of the pureblood families, especially those in Slytherin. My father expects me to join Him, though I am less than thrilled at the prospect."
Narcissa nodded. "That my cousins and my betrothed are of the same view point makes me happy. Family has always been very important to me, and I would go against anyone's beliefs to protect my family."
There was a short silence that followed the sixth-year's statement, which was broken by Severus. "So, we've heard from everyone but Lily."
"Me?" Lily thought about what she could say. "I have an older sister who resents the fact that I am magical, and she's not."
"Resents isn't strong enough a word. I would say hate tinged with bitterness." Lily tried to interrupt, but Severus wouldn't let her. "No, Lily. Don't try to deny it. I know she's your sister, but it's true."
The redhead sighed. "All right, Sev. You're right."
Remus looked around at the three other Gryffindors and the four Slytherins. "Well, we've heard from everyone, and I, for one, have a new perspective on others."
"So do I," the Black brothers chorused.
James nodded. "Same here."
"I agree," Lucius and Narcissa said in unison.
"Ditto," Lily added.
"Yes. I just hope this puts an end to the vicious tricks you tend to play on Slytherins, specifically me and Regulus," Severus put in.
"I promise not to play any vicious pranks," James replied.
"The same goes for me," Sirius added hesitantly.
All of the sudden, the door to The Room of Requirement opened. Recognizing what that meant, Remus and Lucius returned the wands to their owners. All eight students stood up and started exiting the room. After they exited the room, the door disappeared. As they parted ways with the Slytherins, Remus turned to Sirius and asked, "Did you really mean what you said back there?"
Sirius grinned. "Maybe."