Author's note: This story's idea came about after I finished binge-reading Chainsaw Man and read a bunch of Harry Potter fanfic. What you see before you is the most sense I can make of the odd dreams that ensued. It's not a crossover fic by any means, but you'll see some general ideas and tropes from the other series pop up here and there.
Before you read further, I will warn you that there is some disturbing imagery in this story, mostly in the form of body horror and descriptions of Lovecraftian beings. I don't think it warrants an M rating, but if you don't like that sort of thing then I don't recommend reading this.
I don't own Harry Potter.
In the darkness beyond the borders of what we call 'reality', there exist the Adversaries. Personifications of the evils of all life, they exist in the pursuit of a singular goal: the complete and total extermination of all living beings. They gnaw at the roots of Yggdrasil and claw at its branches, hoping to bring down the Great Tree. Among the Adversaries are familiar evils, such as despair, emptiness, and temptation, but also evils that mankind has no name for, such as kshung'tli, an evil that plagues the seven-limbed beings on the world Sz'lavaes when its three suns set.
What stands against the Adversaries? Why have they not destroyed us, clawed through the Tree with their shadowy hands and brought all life into their dark maw? Between us and them lies the Ally, a spirit of virtues, among them Hope, Justice, and Love. Each living world has its own Ally, and it takes a host within whatever being best embodies its ideals. Over time, the host and spirit become one, and when the host dies, the spirit finds a new host. That host is usually a fully-formed being, aware of the virtues and with understanding of the evils. Yet one time, the being on Earth who best embodied the ideal of Hope was naught but an infant. And so, he will take time to truly awaken, to become a proper host of the spirit.
"Wake up."
Harry Potter blinked his eyes, rising from an unsettling dream. The Voice was trying to talk to him in his dreams again, something about a great destiny he had to fulfill. He wasn't exactly sure, as the dream was quickly fading.
Ah, yes, the Voice. It had been Harry's sole friend in his seven years of existence. Though he could neither see nor touch it, he knew on some level that it was as real as the walls of his cupboard. The Voice didn't always sound the same; it was sometimes masculine, sometimes feminine, sometimes neither, sometimes both. It could sound to him as though it was the voice of one or of many. Yet still, Harry knew in his bones that it was still the Voice, no matter how different it sounded. And it was always warm and friendly, promising him that he had a future beyond being the Dursleys' chore boy and whipping boy.
He had first heard the Voice when he was around four or so. He'd watched one of Dudley's television programmes, something about a hero fighting for justice. He'd spent the night afterward trying to understand what was right and wrong, and concluded that the Dursleys were wrong. After all, they acted almost as bad as some of the bad guys from the show. When he questioned why there wasn't a hero coming to save him, the Voice first appeared.
"Get up, boy!" Petunia's shrill voice jolted Harry out of his mediations and reminded him that his hero and his future were yet to come. "That bacon isn't going to cook itself!"
"Coming, Aunt Petunia," Harry responded, opening the cupboard door as quickly as he could. It wouldn't do to be too late, as Dudley tended to demand his bacon as soon as he got downstairs, and the Dursleys tended to let Dudley vent his anger on Harry.
With haste, Harry prepared a breakfast of bacon and eggs. Despite his best abilities, the bacon ended up slightly burnt around the edges, and so Harry prayed to whatever higher power was up there that Dudley wouldn't care and would just wolf it down.
True to form, Dudley sat himself at his usual seat and started shoveling his breakfast into his mouth, forgoing the use of utensils in order to send food down his gullet faster. Harry watched on the verge of gagging at the disgusting display, mentally comparing Dudley to one of those zombies he'd seen once late at night on the telly.
Vernon wasn't much better, though he at least used a knife and fork to move his food instead of his bare hands. Petunia, on the other hand, nipped carefully at the bacon like a bird, taking small, precise bites at her eggs before moving on to try the bacon. After lifting the first piece into her mouth, she frowned.
"This bacon seems a little bit burnt, doesn't it, Vernon dear?"
Vernon, who had at this point cleared his entire plate, grunted an absentminded affirmative. "I suppose so."
"Then I think our esteemed cook here will need another lesson on the value of hard work, don't you think?" Petunia suggested.
"I agree," Vernon said, turning to face Harry. "Boy! You'll be out in the back preparing the firewood this morning! You'll get your breakfast once you finish with the wood."
"Yes, Uncle Vernon," Harry said meekly. The dark-haired boy quickly exited the house and took the hatchet from the stump that usually held it, then made his way over to the logs.
Punishments like this one were the worst, in Harry's opinion. When Uncle Vernon decided to beat him, he'd be taking a few lumps and then that was that. With this, however... he'd be working hard for hours, growing weaker every minute as his stomach rumbled. When he did finally finish, Vernon would criticize the job he did, and then he'd be given far less food than he would need after such exertion. At least the Voice was active today, so he wouldn't be entirely alone.
Voice, he thought. Is there a way I can make this task easier? He'd never asked something so direct before, but from what Harry remembered of his dream, he was supposed to be awakening to his grand destiny soon. Surely a hero wouldn't have a difficult time splitting logs.
There is, the Voice responded. It seemed to be more masculine today, with a tone similar to that of an instructor. I am glad that you asked. Close your eyes and focus on your hope for the future.
That'll help? Harry asked, skeptical. Then again, the Voice had never led him astray before, and so he closed his eyes and thought. The Voice believed in him and his future, and he remembered the warmth he felt when the Voice reassured him. That warmth spread from his core, running through his body, until every inch of him was infused with it.
Now push the feeling you feel around your hand. Imagine it giving strength as you pull it over like a glove.
Harry did as the Voice instructed, feeling the power form around his hand until it seemed to hum. Opening his eyes, he found that his hand was glowing faintly with a white light. Experimentally, he chopped at one of the logs in front of him. The log split in two with a loud crack far more cleanly than if he had used the hatchet.
"This is brilliant!" Harry exclaimed, staring at his palm in wonder.
This is your birthright, the gift of Magic, the Voice explained. You can use this power to enhance your strength and speed, and with more practice, you can use it for more creative applications as well.
"Amazing," Harry breathed. Guess I'd better practice, then, he thought, before chopping another log in half with his hand. For the next twenty minutes, he split log after log, alternating hands and trying to get as quick and clean a cut as possible. Harry marveled at how easy the task was. What would usually take him hours of hard labor to do as an ordinary person was now as easy as a walk in the park! He smiled at the easily split logs before jogging back inside.
"Uncle Vernon, I've split the logs," he said, trying to keep the grin off of his face.
"Really, now?" his uncle said. "Let's see them, then. You better not be lying to me, boy!"
Harry silently led Vernon out to the back, where the wood lay in a neat pile, split and ready for use as firewood. Vernon surveyed the pile for a minute, poking at the logs, before turning and asking Harry a single question.
"How did you do it this quickly, boy? And why does the hatchet seem to not be used?"
Harry paused. He hadn't thought this far ahead, and knowing his uncle, telling him 'I used magic' would be grounds for a beating. "I, uh," he stuttered, trying to figure out a way to explain what he had done without mentioning the 'm-word'. "I split them with my hands, like they do in karate movies," he explained, hoping that Vernon would buy it. After all, real people sometimes did get strong enough chop wood or even stone with their hands.
Unfortunately for him, Vernon wasn't having any of it. "I told you that such freakishness isn't allowed in this house, boy!" Vernon roared. "Just like your good-for-nothing parents, thinking you're better than all of us. I've half a mind to beat you to a bloody pulp now, freak!"
Harry shrunk back. "I'm sorry," he mumbled. "I..."
"Sorry?!" Vernon exploded with rage. "I'll show you 'sorry'!" A meaty fist rushed towards Harry, who nimbly dodged out of the way, then blinked in surprise. He hadn't realized that his body could move like that.
"ENOUGH!" Vernon roared. "I'll break all your bones, freak!"
Be ready, the Voice warned Harry. A monstrosity is coming.
This was the first time the Voice had given him a direct warning. Never before had the Voice expressed anything other than comfort or instructions to him. A chill ran down Harry's spine as his uncle's right arm twisted towards his body in a manner that shouldn't be possible. Vernon's meaty fingers dug into the skin of his own chest, ripping into it and pulling out a handful of ribs, which straightened and elongated, transforming into spears of bone that fused with Vernon's fist. Out of the cavity in his chest came not blood but more flesh, forming into a third arm. Vernon's face twisted before splitting down the middle, forming a wide gaping maw lined with far too many teeth. His left hand pulled at his back, ripping free a shoulder blade that transformed into a shield whilst yet another arm emerged from the hole.
The monstrosity that was once Vernon roared, letting loose a terrible sound that promised pain and death to all who heard it.
"What is that?" Harry asked the voice.
A demon, the voice responded. Be ready to fight. You will need to kill it by destroying the heart.
The demon raised its many spears of bone and charged, looking like a twisted mockery of a medieval knight. Harry drew on his magic once more, coating his arms and legs in it, then sprung over the demon before it reached him and twisting in the air so he landed behind it. He aimed a jab with his hand at where he knew the heart would be, but the demon's fourth arm was there, blocking the attack. Harry's fingers sank into the thick flesh but couldn't form a clean cut. As the monstrosity swung the arm around, Harry realized that his fingers had gotten stuck, buried in the flesh. Desperate to get free before he was forced into that gaping maw, he twisted himself and planted his leg on the same arm as the one that had trapped his fingers, before kicking into the arm, freeing his fingers with a pop. This, of course, had the side effect of sending Harry flying backwards.
Harry sprawled onto the grass a few meters away from the demon, which was rapidly closing the distance. He struggled to get to his feet, but the demon was faster, knocking him to the ground with a heavy kick. The thing seemed to grin with what was left of its original mouth as it raised its hand with many spears, intent on impaling Harry on them as though it was a fork and he was food on a plate. As the spears came down, Harry saw his opportunity. Channeling as much magic as he could into the tip of his foot, he kicked back, into one of the spears, causing it to crack and making the rest of them miss him by mere centimeters. The demon howled in pain, and Harry wasted no time grabbing the end of the spear and using it to support him as he jumped to his feet.
The demon was attempting to use its third hand, the one protruding from its chest, to dislodge the spears attached to its first hand from the ground. Seeing his chance, Harry leapt forward, magic coursing through his body and ready to strike with the spear. The demon blocked with its shield of bone, but Harry twisted in midair and landed a foot on the shield, using it as a springboard to launch himself over the monstrosity's head and behind it. Harry lunged forward and jabbed with his free hand, which was once again blocked by the demon's fourth arm, but this time Harry had planned for it. Using the arm to gain leverage, Harry swung the spear into the demon's defenseless back, infusing it with magic so it plunged through the flesh, tore through muscle and organs, and emerged from the other side, skewering the demon's heart. The creature shuddered and gasped, before falling limp and plunging forward into the dirt.
Explain, Harry demanded of the Voice. Why did my uncle turn into a demon? What even are these demons?
So many questions, the Voice chuckled. It was now speaking as many. Very well. I will now make you aware of the world's true nature.