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Seven Will Come to Know Eight

Summary:

"Perhaps one day… seven will come to know eight again."

OR, Shadow (my OC) dies, only to return as a demon. She hides the truth from the brothers, trains to control her newfound powers, and returns. But when the brothers see her transformed, will they recognise the girl they once knew… or reject the thing she has become?

Chapter 1: Death

Chapter Text

It had been a peaceful, overcast day at RAD. A few more hostile stares, but nothing too far out of the ordinary. At least, that’s what Shadow thought. Unfortunately, her thoughts were short-lived when the alarms went off, signalling a riot in the school. The warning didn't last long enough before Shadow found herself frozen in the middle of one of the school corridors.

“Stay inside!” someone yelled. “Get back!”

Shadow turned towards the sound of fighting.

She should have run. She knew that. She was only human, after all. But she couldn't shake the feeling of the brothers being stuck in the middle of it all. As she pushed against the tide of fleeing demons, an explosion shook the building, and she saw it clearly then: not the violence, but what it meant.

“KILL THE HUMAN! WE DON’T WANT THEM HERE!” The yells of a particularly large group of angry demons flooded the yard.

All seven of the brothers were standing opposed to the group in an effort to calm the student body down. The faculty already had their hands full getting the other students to safety.

They came in numbers, and all-out war broke out.

Shadow ran towards them.

The brothers were surrounded, backs nearly to the academy walls, magic blazing as they fought to hold the line. Lucifer stood at the front, wings unfurled, blood dripping off the feathers on his back. Mammon darted in and out of the fray, stumbling through the wet grass after Levi had summoned Lotan and flooded the entire field. Even Beel looked strained, breathing hard between blows.

They were powerful, but it didn’t matter.

Even the seven great rulers of Hell were struggling; for every demon struck down, two more stepped forward.

Shadow stood at the edge of the commotion. “Has my presence really caused this much hatred towards Diavolo?”

Shadow watched in horror as her newfound family were being overwhelmed. Then, before she could think, she ran right into the open space between the brothers and the encroaching horde and raised her voice.

“STOP IT!!!”

The enraged crowd momentarily paused.

“This isn’t what the Devildom stands for!” Shadow cried out.

Someone laughed. Someone else snarled.
A demon near the front turned, eyes sharp and disdainful as they landed on her. “You,” he said, as if the word itself were an insult. “You’re the reason for this.”

Shadow didn’t flinch.
“If you want to destroy Diavolo’s vision,” she said, heart hammering, “then you’ll have to go through me.”

She felt foolish as soon as she heard the words leave her mouth.

She had no shield. No strength to back up the defiance burning in her chest. But she stayed where she was, legs trembling against the dark grass, because this—this belief, this refusal to yield, was the only power she could ever claim.

The blow came from the side.

She didn’t see who struck her. She just felt the sudden, crushing force that stole the air from her lungs and sent her sprawling across the courtyard. Pain flared sharp and immediate, blooming through her ribs as she hit the ground hard.

The brothers shouted her name in sync.
She tried to push herself up but couldn’t.

The world tilted. Sound blurred. Another impact landed close enough to rattle her bones, and she felt something warm spreading beneath her, soaking into her clothes.
Blood.

Diavolo arrived at the battlefield, seething with rage. He and Barbatos were quick to subdue the remaining demons as the brothers ran to Shadow.

“Hang in there, Shadow.”
“Beel, put pressure on the wound.”
“Stay with us, sweetie.”

She fought hard to stop her eyes from closing, but her whole body felt cold and heavy. Slowly, darkness crept in.

What’s going on? I feel warmth encasing me. My eyes won’t open. I’m so tired.

 


 

Shadow came back to awareness in pieces. Her chest ached, and she could taste iron at the back of her throat. Heavy bandages were wrapped tightly around her torso. Every breath was a struggle, as her lungs refused to expand.

She forced her eyes open.

Golden walls rose above her.

The Castle. She knew it instinctively, even before she registered the presence beside her bed. Diavolo stood there, hands folded tightly in front of him. His usual warmth was gone, replaced by something dark and grim. Barbatos lingered just behind him, expression unreadable as ever.

Shadow tried to speak, but nothing came out except a suppressed, bloody cough.

Diavolo noticed immediately, lowering himself so they were at eye level. “Shadow, don't try to talk,” he said softly. “Save your strength.”

She searched his face, dread curling in her stomach.

Barbatos stepped forward. “You have lost a significant amount of blood,” he said calmly. “Your lung has been punctured. Our healers have slowed the damage, but it is not enough.”

The words settled heavily between them. Shadow understood.

She had known it was bad. She had felt herself slipping, the world pulling away, no matter how hard she clung to it. Still, the confirmation was enough to shatter her completely.

So this is it, she thought, tears pricking at the edges of her eyes.

“Shadow,” Diavolo continued, “this happened to you because of my carelessness. I am deeply sorry.” Diavolo looked over to Barbatos before returning his gaze to her broken figure. “There is only one thing I can do for you now.”

Shadow looked up at him.

“Shadow, if you say yes to this, there will be no going back… Would you like to continue living here in the Devildom as a demon?”

“W-what?” Shadow managed to cough out.

Diavolo’s expression changed. “I can change you so you may become one of us.”

Shadow stared at the ceiling. She thought of the brothers. Of RAD. Of the fragile bridge she had tried to stand on, even as it cracked beneath her feet.

If she died now, she would become nothing more than a story. A cautionary tale. Proof that Diavolo’s ideals were naïve.

If she lived, however—
Shadow took a painful, shaky breath. “P-please, Diavolo. Do it,” she replied.

Diavolo’s face changed. Maybe he hadn't expected Shadow to be so willing to turn into the very being that caused her untimely death. Even Barbatos looked away, unwilling to accept that, even with his powers, there was nothing he could do for their precious human.

“I cannot guarantee that this will be a painless process,” Diavolo stated.

Shadow could only smile at the prince, hoping it would convey her conviction.

“Close your eyes, my dear,” were the final words she heard before she felt another wave of searing pain course through her body. Shadow let out a scream of agony before returning to the darkness that had taken her moments earlier.

 


 

When she woke again, it was to the soft click of a door opening.

Barbatos stood at the foot of her bed, hands folded neatly behind his back, as if he had been there the entire time.

“You have remarkable timing,” Shadow murmured.

He bowed his head. “Welcome back, dear Shadow. How do you feel? I must say, you look positively stunning.” Barbatos handed her a mirror.

Shadow’s eyes widened as she took in her new appearance. Her hair had turned white like Mammon's, and her eyes were a vibrant purple. It reminded her of the twins. From her head protruded a pair of curled horns that made her look like a ram.

The biggest shock, however, was behind her. From her back unfurled wings made not of flesh or feather, but of darkness itself—black glittery smoke shaped into something that resembled wings.

“Is this… really me?” Shadow stared in shock, then half-smiled and handed the mirror back to Barbatos. “Say, Barbatos, do the brothers know?”

“No, but I shall inform them immediately,” the butler replied.

“No.” The word came out sharper than she intended.

He paused.

Shadow swallowed, the movement still painful but no longer unbearable. “I’m not ready,” she said. “For them to see me like this.”

Barbatos studied her for a long moment. Then, without argument, he nodded. “Very well. For now, I will let them know that you are yet to wake.”

“Thank you, Barb,” Shadow smiled.

 


 

Breakfast at the Castle was different from what Shadow was used to.
Light streamed through tall windows, illuminating polished stone and neatly arranged dishes. Diavolo chatted lightly, as if nothing were wrong, while Barbatos poured tea with steady hands.


Shadow’s fingers trembled around her cup.
The pressure inside her built without warning—an invisible weight pressing outward, bending the air, pulling at everything around her. Plates rattled. The table groaned.

“Shadow—” Diavolo started.

The room imploded.
Glass shattered, stone cracked, and gravity itself seemed to twist violently inward. Shadow cried out, clutching her chest as the force surged beyond her control. Diavolo was thrown back, catching himself against the wall with a laugh that sounded more surprised than pained. Barbatos hit the floor hard, blood streaking his temple.

The power vanished as suddenly as it had come.
Shadow dropped to her knees, shaking. “Oh my—I’m sorry,” she gasped. “I didn’t mean to—I didn’t know—”

Diavolo brushed some chunks of the wall from his shoulders, grinning despite the chaos. “Ahaha! That was exciting.”
Barbatos rose calmly, adjusting his gloves as if his injury were a slight inconvenience.

“Shadow… perhaps it would be best if you studied how to control your powers with someone who has experience with gravity magic.”

Diavolo laughed. “Indeed. Well thought, Barbatos! Luckily, the one in question owes me a favour.”

“There is a witch,” Barbatos continued. “Maddie. You may have heard her name cursed by Mammon on many an occasion. She lives on the outskirts of town. She can teach you control.”

A witch?
Shadow hesitated only a moment before nodding. “Yeah, okay.”

Then, quietly, “Diavolo… could you please tell the brothers that I’m dead?”

Diavolo stilled.

“They can’t know,” she said. “Not until I can stand in front of them without hurting them.”

Diavolo closed his eyes.
And agreed.

“Barb, please… let them know,” Diavolo said softly.
Barbatos inclined his head, expression calm as ever. “Of course, my lord.”


Without another word, he moved through the halls, silent footsteps echoing in the empty spaces.

 


 

Barbatos paused at the entrance of the House of Lamentation’s living room. Streaks of light fell over the furniture, casting long, warm beams across the dark floor. Lucifer was at the table, papers spread before him, but his hand had stopped mid-note. Mammon lounged on the couch, pretending to scroll through Devilgram, but his fingers twitched nervously. Leviathan fiddled with a handheld console, eyes flicking up every few seconds. Beel stopped eating, and Belphie sat up, lifting his face from his pillow. Satan stood in the corner, sipping his tea with calm precision, but the slight stiffening of his shoulders betrayed him. Asmo rushed over to Barbatos. “Is our lovely Shadow okay?” he sang, voice filled with hope.

Barbatos cleared his throat.

“My lords,” he said, voice steady, controlled, “I must deliver grievous news.”

All heads turned instantly. The calm in the room shattered under the weight of his tone.

“Shadow… is no longer with us,” Barbatos continued. “The human you once knew is gone.”

Time seemed to stop.

Mammon’s jaw dropped. “N-No… that can’t—” His words faltered, replaced by a strangled, desperate sound. He leapt to his feet, pacing, hands running through his hair. “She can’t be… she can’t be gone!”

Lucifer’s pen dropped from the table, eyes narrowing, lips pressed into a thin line. Every muscle in his body tensed as if bracing against a blow. He didn’t speak, didn’t blink—just stood rigid, in disbelief.

Leviathan’s console clattered to the floor. He sank to his knees, staring at the scattered pieces, mouth slightly open, voice caught somewhere between a whisper and a sob. “Shadow… no…”

Beel’s arms fell to his sides. He swallowed hard, blinking rapidly. “She… she can’t be… not Shadow…” His voice was quiet, stunned, weighed down by the sudden absence of someone he had always counted on. Belphie gritted his teeth, wrapping an arm around his twin.

Satan remained standing. He did not speak. For a long moment, he merely watched, processing this grave news.

Asmo started silently crying.

Barbatos observed them all calmly, letting the shock settle. Then, almost quietly, he added, “Perhaps one day… seven will come to know eight again.”

The room fell into a heavy silence. Not a single brother moved. Not a single word passed their lips. The weight of Shadow’s absence pressed down on them, absolute and unyielding. Barbatos straightened, adjusted his gloves, and departed without another sound, leaving them alone with their grief and the eerie echo of prophecy.