Doom Days (Harry Potter/MCU Crossover)

Pre-Chapter A/N: I think we're at the point where it is officially no longer cool to say Happy New Year! Either way, I hope you're all still keeping up with your new year's resolutions. I'm just getting started on mine (still). Here we go with the fourth chapter of 2025. Lovely to have you all here, and I hope you enjoy this one. If you do, feel free to head over to patreon (https://www.patreon.com/c/Oghenevwogaga) and read the next two chapters- I update there on a daily basis so there's always something for you to read. It's also a new year, so this is probably the best time to buy an annual membership on my page, if you're the kind of person that would do well with one. Have fun. 

"This is a terrible idea" 

"Do you want to be an animagus or do you not want to?" 

"I want to be an animagus, but getting stuck in the body of a beast is not something I particularly fancy, Sirius" 

"I have a wand, Harry. Ill-fitting as it might be, I can get a good enough job done with it to turn you back if you get caught". 

"Speaking of that, why haven't you gotten a new wand yet?"

"Helloooooo. Wanted man here. Escaped Azkaban tenants can't just go waltzing through Diagon and into Ollivander's to buy new wands, can they? The ministry probably snapped mine after tossing me in Azkaban". 

"For Heaven's sake, Sirius. Where are you?"

"Hogwarts." I facepalmed at the reply. 

"But more specifically?"

"The Room of Requirement as you called it, why?" 

"And what do you require, Sirius?" I said leadingly and his eyes widened. 

"There's no chance that works" He said. 

"Well, there's only one way to find out" I said and thought about a specific set of instructions. And then, as if like magic, sticks of wood began to rain from the sky. 

"I can't believe you're making it rain wands. How the fuck is this room making wands?" 

"Making wands? Don't be ridiculous. It's a powerful enchantment, the one on this room, but the founders were wizards not gods".

"But….the wands?" 

"Oh, there's an enchantment on the room. Anything lost in Hogwarts will find its way here in time. A thousand-year-old castle that has probably seen millions of children? There's a lot of lost wands to go through" I said as the rain stopped. 

"And how exactly are we going to sort through so many wands? There have to be a thousand of them at least."

"Oh, please. I only asked for wands that were fully intact and functional with a chance of being compatible with you. It's a couple of hundred at the very most." I retorted with ease. 

He looked around us, probably finding that my words were broadly correct, and nodded. 

"So how do I do this? Just give each one a wave and see what happens?" 

"Exactly" I said with a smirk building and just waved my wand once to pick up all the wands and gather them into a pile. 

"You're getting better at that" Sirius said, and I resisted the urge to preen at the praise. Two-Thirds of my person was made out of attention starved teenagers who absolutely craved positive reinforcement from authority figures, so it was much harder than I made it seem. 

"Of course I am. I've been working at it for a while". 

"I see. That's good then. I don't think either James or I got to the level where we could start messing around with stuff like that until we were well out of Hogwarts" what he was referring to was spell-less spell casting, which as an art had one of the most counterintuitive and complicated names out there. What it was, in truth, was simply using one's magic to influence reality without using something as specific as a spell. The wand was still necessary for me, but I knew that for wizards like Voldemort and Dumbledore, telekinesis without a wand was the bare minimum. 

"Like the two of you are a standard to follow" I said, still feeling sullen at the day's revelations. 

"I'll have you know we were completely awesome wizards in our time. We even became animagi, unlike a certain someone here" He said. 

"1 in 10 wizards are incapable of the transformation" I quoted the stat with invisible shame building. 

"Know what else 1 in 10 wizards struggle with?" 

"You're gross, and I'm fourteen" I pointed out, but he had already headed off to the pile of wands.

"Just give each one a wave. Don't actually try to cast anything, or you might blow both of us up. Some of those are probably really temper-" I hadn't even finished when he dropped one wand with a jolt like he had been shocked. 

"— emental" I completed. 

"Go do your ritual while I work with this" Sirius said, picking up another wand and probably feeling uncomfortable with me being present for what was an intimate process to most wizards. 

I nodded and walked to the other end of the room. Sirius' blood replenishing potion was red just as the book required, with the only difference being that where the book stipulated a deep red, his was so light that it was almost pink. Still, my senses told me the potion was good enough to drink, and the book also said that failure to meet the colour requirements wouldn't be fatal with this particular potion. I chugged it down in one gulp, doing my best to ignore the coppery taste in my mouth. 

Next, I moved towards a silver bowl and picked up the silver knife next to it. I hesitated for a brief moment at the thought of the pain to come before I drove the knife down, slicing across my palm in a smooth movement and placing the bleeding palm into the bowl.

The bloodletting ritual was a fascinating bit of magic, technically legal, but dark as they came. It was the ritual that served as a solution to blood curses for the most part. Sounds strange to you? Well, centuries ago, blood curses had been a massive problem. One naughty wizard from the Grimm family had discovered how to cast nasty curses with small amounts of blood and had basically cemented his house's position at the top of the wizarding world by virtue of that ability alone. The fear of being cursed from miles away left most too scared to even risk offending them.

And then came Cordelia Abbot, a brilliant charms mistress by all accounts, and a very tricky witch by most. She took on the issue of the blood curses because the rumors at the time had been that Janus Grimm, the Heir to the Grimm family at the time had chosen her to be his wife, and she could not say no because of the threat of her gamily being cursed. She created the bloodletting ritual which allowed one to divorce any connection between the blood within their body and any external collections. It would basically render any blood that had been taken from the wizard as useless. 

Why was I taking so long to do the ritual? Well, for one, the ritual Voldemort needed to bring himself back had to take place under a full moon or equally rare celestial event, and that was still a week away so I had no need to rush. For second, the ritual hurt like a motherfucker. In case you're wondering, the pain is the reason I've begun explaining things to myself like I had an audience. I just had to make sure my lips kept moving in the long latin chant that was required. 

Tom Riddle had learned of the ritual after Anastasia Carrow had cut him in potions and threatened to make him pay for showing her up in defence with a blood curse. I learned the full gist of it when I asked the room to provide me with all the information it had on the ritual. One part of the story Tom Riddle hadn't known was that Cordelia Abbott had been a fifth year Slytherin when she designed the ritual, and Janus Grimm had been well into his sixth decade when he'd set his sights on her. Needless to say, no one had shed many tears when the Grimm family had been slaughtered to the man a few decades later when they set off the ever mercurial House Black. 

As I said the last sentence of the long incantation, I felt my injury begin to scab over, the sign of a successful ritual and breathed a sigh of relief at not having to go through that twice. 

"That looked intense" Sirius said with a whistle, making me jump in my skin as I'd forgotten he was even there.

"Found a wand, yet?" I asked, wiping off some sweat from my brow and the few tears that had built in my eyes. 

"Yup. Elm and something nasty inside. Can't tell what it is, but this one feels like it wants to rip, tear, kill, and all that fun stuff" He said, before reaching out and grabbing my wrist. He stared at the scabbed cut on my palm before waving his wand over it. Nothing happened, and I watched his face set in a harsh frown. He jabbed his wand this time, and only the fact that I did not have my own in hand prevented him from losing his as I felt my hand erupt in pain. 

It was short-lived, however, as the scabbed wound quickly knit itself shut. 

"Was that a dark healing spell?: I asked, curious about the emotions that had flashed on his face as he used it. 

"Don't be ridiculous. The dark arts do not heal. They exist to take and destroy and pervert everything they touch." He said with tone as dark as his name. 

"I find that to be a bit limiting, don't you think" I said, commenting on the viewpoint before I noticed the way his expression morphed. His grip on his wand tightened, and his lips were pressed so closely together that one would be forgiven for mistaking them as a single line running across his face, breaking the furious visage into two halves. His eyes, grey as the clouds, were wide open as he stared me down. I absently noted that he needed a haircut and could just barely stop myself from chuckling at the ridiculousness of the observation in light of the fury he was displaying. 

"I won't tell you not to use dark spells. Morgana knows I know hundreds of them, but the real dark arts are things to beware. You have to run from them. People like my cousin Bellatrix, or even Wormtail, they're par for the course, not the exception. The dark arts will turn you into a hollow shell of yourself if you let them" I nodded at the words, silently changing the classification I'd given him in my own head. 

"Good. Don't forget it. Anyway, that was just a basic healing spell I picked up when I was younger" He said. 

"How young?" I asked, trying to move away from the awkwardness of the previous conversation. 

"Too young. I'd been stubborn as a child and dear old mom couldn't deal with it. She punished me in cruel and unusual ways, and when she was done, my father, Orion, would sit with me and heal me while trying to convince me that she wasn't always a crazy bint." He chuckled, but the spark of bare laughter never appeared in his eyes. 

"I see" what could one even say to something like that. At this point, the part of me that was Doom was the only person here who'd had anything even vaguely resembling a normal childhood, and he'd done multiple orphanages and foster homes before being permanently adopted. 

"Enough of my dear old family, what do you say we test out my new wand? I've been watching your training and I think it's time for your Dogfather to show you a few tricks". 

"Dogfather? Really?"

"Knew it was terrible the second it left my mouth, don't worry" He said, and I nodded while giving him a skeptical look and taking my stance. 

"Of the four of us, not that Wormtail really counts as worth anything, I was the best duelist by a bit more than a shade, so I'll go easy on you" The former Marauder said as he took his own stance. 

The elm wand lashed out without any warning, and I found myself deflecting several spells that could barely even be considered as hexes. The only issue was that there were too many of them, I thought to myself as I fucked up deflecting one pink curse and had to find the time to flick my wand and dispel the toenail growing hex that made it through. I put up a shield that took the next volley without problem but had to reinforce it as a deep orange that I recognised as the blasting curse, Confringo, shot from his wand with little fanfare. 

The confringo was followed by another and then another, forcing me to drop my shield in favour of deflecting the powerful spells, but then Sirius switched back to using harmless jinxes and hexes to overwhelm my speed. So that was how it was. I allowed the next two spells to hit me, and tore up the ground with a heave, allowing the rest of his spells to wash away against my wall. A silent finite ended the hiccups that had been building and had my armpit hair reduced back to a manageable level. Did I even want to know why there was a jinx made solely for forcing armpit hair growth? 

I pushed at the wall, banishing it forwards in pieces as Sirius' blasting curse tore it apart just as expected. He waved his wand, forcing the pieces of rocky shrapnel to slow almost to a halt as they approached him. A whispered incantation and a twirl of my wand turned all the rocks into scorpions of varying sizes. He tried to banish them to the side, but I pushed against it with my own banishing charm, sending the scorpions through his impediment jinx and right at his feet. Cool as ice, his wand lashed out and set the scorpions on fire. 

Fire that coalesced around the tip of his wand until it had formed into a whip. The fire whip lashed out as he sent it at me. I lifted my own wand and froze the flames that were about to touch me right before they did, and caught the fire whip with my right hand. Holding on to his whip, I sent several piercers heading right his way. 

I felt my flame freezing charm break a second too late as my hand erupted in pain. I dropped the whip just as Sirius spun out of the way of the piercing curses I retaliated with. His next spell was a dark grey one I did not recognise, and so I risked shielding it instead. The spell tore through my shield like it wasn't even there and connected with me with no resistance. I felt my muscles spasm like I was in the middle of a tough workout and so could do nothing except eat a bludgeoner right to the skull. 

"What the hell was that?" I asked upon regaining consciousness. 

"A bludgeoner. I've seen you use one a few times, don't tell me I hit you hard enough to give you amnesia".

"Don't be cute, Sirius" I scowled up at his smiling face. 

"A muscle contracting spell your Da came up with. He was trying to improve on the masturbation spell to get a more effective…explosion, but this was all we got out of it. It ignores most shields though, so it's perfect for duels" He said. 

"Teach me" I found myself instantly demanding, even as I tried to ignore the image of a teenage James Potter hunched over his penis while holding his wand. 

X-

"Have you decided what to vote for?" Sirius asked as I sat cross legged before the fire, poring over a tome. 

"The magical duels. It wasn't even a contest. If I'm going to be fighting Krum with staves, then it will be after I've got a ritual or two under my belt" I said. 

"Have you decided which ones to do? I still don't see why you're refusing the Black Four. James and I did them and look at us." He said. 

"Well, I'd want something that would give me a bit more of an edge than what you two had going for you." 

"You can't get benefits like that without some serious cost, Harry. I've told you. It's impossible." 

"Well, Rowena Ravenclaw would disagree. She was on to something." I said, as the tome's words began to sink in.

"Wait. Rowena Ravenclaw wrote that? THE ROWENA RAVENCLAW?" He asked, sounding gobsmacked. 

"Well, she didn't write the book itself. It's the journal of an early Hogwarts Headmistress, but she had been working based on notes from Ravenclaw. Ravenclaw had theorized that there would be a way to create an even more powerful form of ritual by taking into account the old wild magicke rules. Phyllida Spore, the headmistress of the day, had a thing for herbology and figured that if one were to cultivate a sufficiently powerful plant, then it could be used in an assumption ritual." I said to him.

"Assumption ritual? Why does that sound spooky?"

"No. It's like a standard potential unlocking ritual— the kind that you and James did in your time, except focused on not just unlocking the upper limits of one's potential but assuming the strengths of a magical being" I said. 

"I don't think either of us can cultivate any magically powerful plants, and most of these don't even exist in Britain anymore. The strongest thing you can get here is a Mandrake." 

"I agree. But she theorizes that you can do the same thing with a magical creature, except not by raising it, but by slaying it in combat." 

"So you want to go monster hunting?"

"I don't need to. I already slayed a powerful magical beast, remember?" 

"Cwn Annwn? But the ministry took the body. How is this ritual of yours going to work?"

"Doesn't matter. My magic remembers. The same way my magic remembers that I killed the Basilisk. I just need something to represent the hellhound and the basilisk. It should be enough. I don't think I'll get as much from the Hellhound as I will from the basilisk. The fact that I had help with the hellhound should make it worth less than the Basilisk in the eyes of magic." 

"This sounds like dark magic" Sirius said, trying to be flippant about things, but I wasn't going to be falling for that. 

"It isn't. It's old magic, wild magic. When the druids of the Old English Forests ran into magical beasts and defeated them, they would bathe in the blood of those beasts to strengthen themselves and take on the traits of the beasts. There used to be an adulthood trial among the Norse wizards of old— they would seek out a magical beast before their maturity and slay it in single combat. In the end, that creature would be used to strengthen them for their maturity. It's ancient, but not dark Sirius. Nothing is being sacrificed here. Well, that's untrue. The value of the ritual comes from the fact that I risked my life to kill the beasts, but that's already happened, so why not gain the benefits of it?" I could see that he was still not completely convinced, but he conceded the argument all the same, and that was the best I could ask for. 

A/N: Harry and Sirius shenanigans for the chapter. Loving his role in this. As always, the following two chapters are up on pa-treon. If you just want to read complete chapters and not my work in real-time, then feel free to purchase this story as a collection on my patreon(https://www.patreon.com/c/Oghenevwogaga) page so you get to read each chapter after I finish it and not neecessarily the daily updates available with a regular patreon (https://www.patreon.com/c/Oghenevwogaga) membership- nice way to support this story and me while you're at it. Enjoy!