Original idea partly by icecatfire.
Staring at the Bottom of the Glass (HP/MARVEL)
Sirius Black was no fool. He knew that he should not mess with clearly magical artifacts that he had exactly no information about (but he was bored, so sue him).
James, Peter and Remus were all attending Care of Magical Creatures right now, a subject he had not elected. Why would he when Ancient Runes, Arithmancy and Muggle Studies (to annoy his mother) were offered?
Normally, he would be sitting in the last one, but the Professor was ill or something (if Sirius was honest, he did not particularly care).
Lacking anything else to do (please, as if he'd still have homework to do), he strolled through the castle. While wandering through a corridor on the seventh floor, he dropped the quill Remus had lent him earlier that week (it made normal ink all sparkly, so it was really far out in Sirius's opinion). He went back to get it, before he returned to his original route.
Or he would have done so, if not for the door appearing out of the corner of his eye.
Now, he was used to such things happening, he had grown up in a magical home after all. Also this was Hogwarts; one could not simply apply logic to the castle.
Curious, he opened the door and walked through it.
He wasn't sure what he had expected—perhaps an unused classroom or something—but this certainly wasn't it.
The room he entered was fairly dark and had a high ceiling; it reminded him of the dungeons and yet not. Somehow, Sirius knew this room. He looked around and spotted a huge bed and countless of books were spread everywhere.
Inexplicably, he felt a strange pull towards one book in particular. It looked really old and was at least the length of his arm.
After barely a second of consideration, he touched it.
Nothing happened, so he tried to move it. Amazingly, the book shrunk enough to fit in his pocket. Sirius quickly cast a Tempus charm and decided to keep it during class.
Over the course of the day, he felt...odd.
If was almost as if he was getting stronger—both physically and magically—with each passing minute.
Which was totally ridiculous, of course.
Only… his friends seemed to feel a difference too.
Remus felt physically stronger; the same was true for Peter, only he felt his eyesight and coordination seemingly had drastically improved as well.
James, however, seemed to notice more and more things, had started to think differently. Oh, he was still James, but it was almost like a more Slytherin version of his best friend—and he couldn't even say anything without being hypocritical as the same thing was happening to him.
That book had to be doing this somehow.
None of them had any idea how, so they decided to get rid of the book.
After all you should never trust a magical book, especially if you don't know where it keeps its head.
When Sirius tried to take the book out of his pocket, however, it had vanished.
The Marauders searched their entire dorm and common room for the book (they even attempted to use a Point Me charm), but it was nowhere to be found.
That night, all of them had weird dreams. They didn't feel like that though, more like old and forgotten memories.
Remus dreamed of gigantic feasts held to his honor and the sense of abandonment.
Peter's dreams consisted of running away and travelling with a circus before gaining a new family.
The dreams of James were always accompanied by a sense of betrayal, hurt and loneliness, despite the fact that they were about experiencing all the luxuries one could imagine.
Sirius himself was falling into a deep and dark abyss with no end in sight.
It was no wonder that he woke up screaming and panting; those images were pure horror and he got the impression that he had only seen a tiny part of it.
Alas, something had changed during the night; not only for Sirius, but for all of them.
All four Marauders remembered.
They were able to recall the memories of their lives before the one they were currently living.
That created a few issues, because grudges apparently did carry over to another life (always nice to know, Sirius/Loki supposed) and there were quite a few between them.
Most people in the school wondered why the Marauders had suddenly seemed to split up, but a few others had an idea why.
As it just so happened, those were the selected few that the Marauders had fled to.
James had seemed to connect to Ravenclaw Thomas Stebbins during a Defense lesson and (after Stebbins got over the shock) were quickly almost inseparable. And (to the amazement of the vast majority of students, staff, ghosts, and portraits) Lily Evans had joined them after a couple of days.
Remus and Peter had a similar experience with Amelia Bones, a Hufflepuff in the years above them
Christopher Daniels, a Gryffindor, had suddenly started to hang out with Regulus Black and Hufflepuff seventh-year Frank Longbottom.
Meanwhile Sirius Black was alone.
"Look, I'm sorry for avoiding you," James (or Tony, he supposed) apologized a week later. "I was still slightly pissed about you defenestrating me and I had just found Bruce again. And Lily is Pepper! But I should not have left you alone. I hope you can forgive me."
"There is nothing to forgive," Sirius/Loki stated confidently (or so he hoped). "I was a dick before."
"Yes you were," James/Tony agreed. "But you know what? So was I! So was everyone else! I could easily have ended up joining you in New York. I have literally no right to act all high and mighty; judging you like I'm any better. The only ones who have that are Clint and Thor, because of the brainwashing and pretending-to-be-dead-ing. The rest of us, however, don't."
Loki/Sirius was stunned. Never, in either of his lives, he remembered someone (other than his mother and children) standing up for him like that. Even if they were only defending him against his very own self.
It must have showed on his face, because James/Tony quickly engulfed him in a hug.
Maybe this would all turn out alright.
Further Plans: A lot.
Requirments if adopted: PM me so I can tell you who is who.
Please tell me what you think!
~Marvelgeek42