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I Summoned a Demon 101: an In-comprehensive guide to Corporeal Demon Do's and Don'ts

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The room is dark and hushed this evening. Izuku’s breathing is quiet, as if he would disturb a resting beast were he to breathe too heavily. His bedroom floor is a ghastly image beneath him- poorly sealed jars of blood and dripping candles littered about a web of bones and salt.

If anyone were to walk in, they would think he was attempting to summon a demon.

It just so happens, that’s precisely what he intends to do. Izuku’s eyes drop to his notes again as he runs an absentminded hand over his forearm. He’s still not quite used to the ridges the scars there form. (Not from self-harm, no- intentional bloodletting. Every drop of blood in this room is his, after all, and proper medical equipment isn’t easy to come by.)

He’s ready for this. He knows he is, but a nervous simmer grows in his belly nonetheless. He’s spent months studying the ceremony, gathering the materials. But even so, he’s never summoned a demon in the flesh before, it’s going to be nothing like the way which he met and bound his current contracts.

It’s due to be grotesque. When he calls the demon, he will first have to expel it from his own mind space- and within the human realm it will have no choice but to make itself a corporeal form with the materials provided, or wither away and die within minutes. No sane demon would choose the second.

They won’t be on good terms, at first- Izuku will have to trick the demon into taking his bond. (It’s not that he fears he won’t be able to, its more that he fears being a master- taking away a being’s freedom. He doesn’t know if he has the heart to follow through) The demon will hate him for that.

Izuku only hopes their relationship can be repaired, over time. (Is it sad, that he’s only ever wanted friends from these beings? He wants to be a hero- he has no use for minions, for pawns.)


Izuku. I know you’re nervous, but we must begin. The moon will only be out for so long.


Shiso’s soft voice hovers in the back of his mind before fading away- words that he can hear that have no volume. Shiso is a friend- his guardian. A demon he has held in contract since the very beginning.

“You’re right, Shiso.” Izuku takes a great, preparatory breath. “Let’s do this.” He runs a finger over his notes one last time. My blood will be your shackles. A warning, not for him, but for the demon. It’s a bitter play on consent- no demon who fails to come willingly will want to be bound- but no demon who is called will be able to resist a human’s blood, freely given.

Izuku steps into the circle and steels his nerves. Shiso’s presence hovers around him- a gentle comfort, a safety net. Whatever may happen to his body- Shiso will preserve his mind.

Izuku shuts his eyes, lifts his hands, and calls . It’s an odd feeling- a sort of lurching in the pit of his stomach, a sort of electric surge rooted deep in his soul. This is the essence of his quirk.

A warrior. Bring me a warrior. He demands it of the void, puts every ounce of his power into the request. He needs something powerful- something loyal and moral- something that will stand with him and be a hero. So, he asks for a warrior.

For many moments, nothing happens. Izuku stands in the still air of his bedroom and listens to the way the walls creak. Doubts and worries begin to trickle into the back of his mind but Shiso whisks them away, allowing Izuku to focus solely on the task at hand. A ghost of a hand ( talon ) cards through his hair and Izuku settles further into Shiso’s guard, projecting his call even further.

Eventually, just as Izuku was about to throw his hands down and give up, something takes the bait.

In an instant, Izuku loses himself to this being. Its soul is nothing but fury- red-hot and roiling and all-consuming Rage . It floods his mind with its sheer force of presence and Izuku is forced out, smashed back, tamped down. For a terrifying instant Izuku fears that he has lost his Place to this being, that it has taken his body and his mind and left him only a soul- trapped out of himself.

But no. Izuku’s steady descent is halted suddenly as Shiso catches him, as Shiso throws up a guard that’s hot and solid like sundrenched steel and shoves the warrior back. (Sometimes, when Izuku is wrapped up in Shiso’s warmth and comfort and sibling-like love, he forgets how powerful he is, how ruthless .)

Izuku breaches the surface of his own consciousness just as the warrior is pushed out , and Izuku feels the phantom feathers of Shiso’s aura flutter across his skin, before the demon fades back, job done. Breathing deep, Izuku prepares for the next stage. Izuku is steely calm and determined. The room rattles around him, shaking papers off of his desks and books from the shelf, quaking jars and bones from their places on the floor as Izuku takes the being- free in this realm but confined to the circle- by the core and shoves , compressing it, confining it, taunting it .

The being rears back, fights against him, corrupts his mind with thoughts of destruction, of terror, of insignificance and ugly hatred and soul-clenching, explosive Rage.

“Come on, you coward! Make a body and challenge me yourself!” Izuku shouts, and once again the demon takes the bait.

The rattling of the room halts as the demon ceases its attack, and the tension in the air drops as the soul of the demon seemingly disappears. For a second Izuku is terrified, convinced that somehow his circle was incomplete, that the demon escaped- until a soul-deep rumble bubbles up, as if coming from the foundations of the building itself. Izuku watches in thinly veiled disgust as the blood and bone littered about the floor begins to move on its own, seeping out of jars and rolling across the floor. When all of the materials have congregated in one place they begin to boil- bubble and pop and roil- as the demon begins to build itself from the inside out.

The room becomes uncomfortably hot as the process goes on- and when the being’s mouth forms out of the mess, a terrified, blood-curdling screech escapes from its half-formed throat. Izuku wants to shut his eyes- wants to cry. What pain is this being in, to make a noise like that?

When the demon finally calms, the room rings in the quiet, the beast’s breath loud and rickety. It squats, bound within the inner circle, quivering in what looks like the residue of extreme pain and panting with exertion. It’s completed corporeal form is humanoid but strange, an amalgamation of the idea of a human and aborted demonic qualities. The creature sits huddled in on itself, head down, spine curled, legs tucked and arms pressed to the ground. Its skin looks thick and leathery, laid across its form in pieces, much like a suit of armor, but colored to mimic Izuku’s own pale skin. Its hands and feet however, sport a darker, ashier tone, that fades up the wrists and ankles. At major joints, the leathery armor hardens into thicker, discolored, elongated spikes, at its shoulders, elbows, knees, and along its spine, mimicking something one might see on a dragon. At the base of its spine Izuku can see a stubby, aborted tail, and short but sharp nubs near its shoulder blades, where Izuku believes wings could have grown. Between the leathery skin plates, and in the softer, inner parts of joints, Izuku can see a softer, pinker, almost velvety material. Atop its head sits a shock of pale, spiky hair, and from its forehead Izuku can just recognize dark, short, and thick horns.

In the time it took Izuku to mentally catalog the demon’s every physical feature, the being had quieted, stiffened, and began to growl lowly. Izuku nearly jumps when the demon snaps its head up, eyes locking on the human. The demon’s face is soft like its inner elbows, but its expression is set in a deep snarl, flashing fang, with fiery, narrow eyes. Slowly, Izuku lifts a switchblade out of his pocket and takes a deep breath, hoping not to spook the demon.

He has only a precious few moments to catch its interest before it surely kills him- its brand new limbs are still unfamiliar, for a brief amount of time the demon is outmatched by Izuku and the fifteen years of life he’s spent growing into his body.

It lurches forward but stumbles, halts, and Izuku takes its hesitation as he can and slides carefully to his knees, baring his neck. He takes the knife and cuts a tentative slit over the flat of his neck. The demon’s eyes zero in on the wound instinctively- its pupils blow wide at the sight of it and its nostrils flare, surely taking in the scent. It takes a careful step forward, wobbles slightly, and takes another. Izuku lowers his eyes and opens his mouth.

“Warrior of Rage.” He whispers. Dominate, surrender; command, trust. The warrior pounces, eyes wild, fangs bared.

My blood will be your shackles.”

It halts, seething, fingers gripping Izuku like a vice, kneeling over his lap, looming, glaring, trembling with want. Izuku breathes, waiting. It has no real choice now. Drink, like its entire being is pushing it to do, or kill him, only to wither away within the confines of this circle for eternity.

The better option is clear, but the demon struggles against its instincts, just for a moment. Izuku is patient, he knows he will come out of this encounter victorious. A broken, unsteady growl tears from its throat, and the demon locks eyes with him. Its eyes scream insults at him- words it doesn’t yet understand how to form- so it only growls, seethes, and bites , digging its fangs into the meat of Izuku’s neck, guzzling blood like a dying man at an oasis. Izuku winces, wobbles, but is grateful.

That was an admission of defeat. With every drop the demon consumes the bond solidifies, grows stronger. Izuku, in return, must declare the terms.

“My blood will be your shackles.” He repeats, holding the demon’s head to his neck, pushing it to drink. “You will exist in me.” He continues. “So long as I live, I will feed your power. So long as you live, you will fight for me. My life is your life, my death yours as well.” Izuku takes a deep breath- the ceremony is nearly complete. “Warrior of Rage.” He tugs on the bond, and the demon lifts its head.

Its eyes are bright with power and defiance, but as its tongue flicks out to lick up a drop of blood that had slipped from its lips, Izuku knows he is safe. He blinks slowly at the demon, smiles softly. You don’t need to hate me, warrior, I will treat you with kindness. I will do my best. The demon looks back, revulsion and confusion marring its features. Izuku fights his despair- now is not the time.

“Warrior of Rage.” He repeats, flooding the phrase with power. “I will give you a purpose. In exchange, you will give me your name. Is this agreeable?” Izuku waits. The demon clears its throat- a raw, grating noise, flexes its jaw.

“Yes, Master.” (Izuku knows not to show weakness in the face of a demon whose name he does not possess, but he can’t help but flinch. There’s no better way to do this- to try to bind a hostile demon with kindness is a death wish. Izuku knows. He knows, but it still hurts. He doesn’t want to own anyone.)

“You will protect the people.” Izuku states.

I will protect the people.” The demon repeats, tone deadly serious.

“I am Midoriya Izuku. Now, demon. Give me your Name.”

Even after agreeing to the terms, the demon hesitates. A demon’s name is more than a series of sounds- it’s their soul- their earthly presence. It’s the audible wavelength of their existence, the strongest binding power over them. To know a demon’s name is to possess it completely- it’s the ultimate power to hold over another being.

Izuku wishes he didn’t need it, but a bond cannot be sealed without the trading of names.

“Give me your name.” Izuku whispers. The phrase is every binding power Izuku holds over the demon- it cannot fight. It bows its head, dominated, and gives it.

It feels like fire and gunpowder and passion, like pride and anger and strength. The name hits Izuku like a landmine, all heat and shrapnel and destruction. “Bakugou Katsuki,” Izuku repeats, and he’s disappointed in the pitiful excuse for a sound in the wake of the sensation he’s still reeling from. Bakugou flinches at the sound of it nevertheless. Izuku smiles, gentle, comforting.

“Bakugou Katsuki. With this the contract is sealed, and your soul bound to mine.”

“Midoriya Izuku. Quit it with that creepy-ass fucking face, why do you keep looking at me like that?” Katsuki barks, and Izuku blinks, startled.

“Uh—what?” Izuku responds, intelligently.

“That fucking- look you have. On your face. Quit it.” The demon’s tone is demanding and Izuku doesn’t know what he was expecting of a freshly bound corporeal demon but it wasn’t this… human. The demon speaks like the kind of delinquent Izuku would find slouched in the back of his classroom at middle school- his spiky, white-blonde hair and large, hooked earrings failing to dissuade the image from Izuku’s mind.

“Um… sorry? I- wait!” Izuku startles as the demon leaps, suddenly, from his place on the ground in front of Izuku to the surface of the boy’s desk. Papers scatter and tear under his large claws, and Izuku is quite significantly concerned about the integrity of the surface of his desk, it could part so easily under the demon’s sharp talons. Izuku tries to stand but quite suddenly realizes precisely how much blood he has lost- and though the wound has already closed- a convenient pro of the bond, Izuku is sure- he’s still hit by some intense vertigo upon trying to move.

“What, stupid human? Don’t want me to tear up your shit? Maybe you should have put that in the contract!” The demon taunts, grinning down at him. Izuku doesn’t try to move again, instead only frowning up at the demon.

“If you’re going to behave like a temperamental child, I might have to add unnecessary rules to the contract after all. I had thought you would be enough of an adult not to tear up my things just because you can.” The demon scoffs down at him.

“Oh, little boy has a mouth on him, hm? You want me to behave? Why don’t you get off your ass and make me ?” Katsuki taunts, dragging a claw threateningly over the surface of Izuku’s desk. The boy furrows his brows. So, we’re going to play that game.

Bakugou Katsuki. ” Izuku says, threading the words with intent. “Stop. Come back over here and sit.” Katsuki pauses, smile dropping from his face. Izuku watches guiltily as the demon climbs awkwardly back, as if fighting his limbs all the while. He didn’t want to make the demon do anything- but to let him do what he wants at this point would be like letting a feral dog loose in the house. Izuku supposes he will have no choice but to loosen the figurative collar as time goes on, and the demon adjusts to his role.

“Alright. Listen up.” Izuku tries once again to stand, is successful this time, since he took it slow, and wobbles over to the desk. He cleans up the salvageable papers and puts them in a neat stack, before flipping through the notebook to the page he had written down rules and stuff just in case he needed them.

“Right. Okay.” Izuku states, looking over his notes.

“Get on with it.” Bakugou growls, plopping back down to his bottom like a puppet with its strings cut. Izuku wobbles back with the notebook in hand and follows suit.

“Alright, so, I’ll just give you the rundown on why I bound you in the first place, I guess. So, uh, I’m an aspiring hero, I mean- I’m going to become a hero, and I can summon “Obviously,” Bakugou interjects. Only slightly put-off, Izuku continues.

“Right, so, usually demons I summon remain like, in my brain, or whatever, and when I need them we just, share brain space or whatever, and I can use their powers, for a price, right, but I haven’t befriended-”

“Tch.” Bakugou snorts. Izuku plows on.

“Uh- bound, any strictly offensive demons, I have two Guardians and one Ally, but no Warriors, so my offensive abilities are lacking, right, and the UA entrance exams are coming up- that’s the hero school I want to get into- and the practical exam is said to be really physical, so I figured my best bet would be to have a partner working with me in the flesh, I’m running out of room in my head, and then I’d be able to have the power of two demons on hand at once, right, so-”

“Stop fucking rambling, you useless waste of space. I don’t give a flying fuck, get to the point.” Bakugou cuts him off again and Izuku stops, blushing.

“Um- right. Okay. so, most important rule, Bakugou Katsuki:” Bakugou snaps to attention at the call of his name, “Do not, for any reason, ever, kill a human. Even if they are the enemy, even if they don’t look entirely human. Don’t ever end a life. That means no mortal wounds. I understand that in some cases, you may need to injure or maim someone in order to achieve a goal, but this is a last resort.  You will not harm humans needlessly… Also, uh, you aren’t allowed to hurt me needlessly either, if you kill me you die, so uh. yeah.” Bakugou scoffs, but nods, and Izuku continues to the next bullet. “Second, you are to protect innocents with your life. Their life comes even before mine. As a hero, your job is to ensure public safety-”

“I object.” Bakugou states, tone entirely serious. “My life is tied to yours, therefore if you die, I die. My priority must be your life before anyone else.”

“No.” Izuku commands. “Bakugou Katsuki, this is an order.” Bakugou shudders, at rapt attention. “You are a hero now. The life of the innocent must hold greater weight than the life of yourself. You will protect the people.”

I will protect the people .” Bakugou repeats, tone full of conviction. Izuku locks eyes with the demon and nods.

“Good. Those are the most important rules, but that doesn’t mean the house rules aren’t also important. Don’t be needlessly destructive- respect my belongings and the belongings of others. Learn to behave within human society- I don’t want to treat you like a bound demon but if I have no choice, I will do what I must. Obey our superiors, as long as their orders don’t directly counteract mine. You will have freedom, with me, so long as you don’t abuse it. I need you to be able to work independently of me, in time. If I can trust you, I will loosen the binding strength of these rules. Okay?”

Bakugou sits silently for a moment, before huffing out a great, exasperated sigh and rolling his eyes. So much for the cooperative attitude. “Yes, Master.” He retorts dramatically. Izuku chokes a bit, coughing.

“Uh, yeah don’t, ever call me that again, that’s weird, um, yeah. No.”