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Sanguinius fixes the universe, (properly, for good this time).

Summary:

In one universe, Sanguinius glimpses the future and lets it come to pass. He dies, the Imperium is broken, and The Emperor is chained to the throne. Guilliman becomes Lord Regent. His brothers die horribly. Humanity is shattered.

In this universe, Sanguinius meets his only biological nephew, (the child of Konrad fucking Curze of all Primarchs), adopts him, (mostly by accident), brings his family together again, (entirely by accident), and avoids the worst possible outcome for humanity thanks to the power of frustration. He also manages to accidentally rewrite reality by doing all of this... no big deal.

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OR, Sanguinius becomes a father to one (1) traumatised child, bitchslaps his family into being better, bitchslaps his father into being better, bitchslaps half the Imperium, and fixes everything with sheer determination. FT, fluff, angst, canon-typical violence, a dead person or three, author favouritism towards dead/dying/traumatised/doomed characters, and a cute child who accidentally wins over all his uncles by being himself.

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OR, Author lost a bet and is now forced to write a WH40k fanfic despite knowing nothing about anything, but they're trying their best. Please believe me.

Notes:

Here's everything you need to know for this fic;

1) Author is new to this fandom and has no clue what anything means or why. Some things might be out of order because of this. Take everything I say as a work of fiction, (of FANFICTION!), and don't take me as gospel. I'm learning along the way, and chapters will be changed accordingly to new lore I learn.

2) This fanfiction is a simple fluff piece, some things might not align with canon. (See 1)

3) I have a massive soft spot for everyone of the Primarchs, except Konrad Curze... fuck that guy. And not in the fun way. So everyone gets to live! Unless they don't. (see 1)

4) In this universe, Konrad Curze had a child. This will be explained later in the story as to how/why, so hold your fingers folks, all will be explained.

5) Most characters will be slightly OOC because I'm going through a writing style rework. I'm aiming for more detail and cleaner conversations rather than lore accuracy, also, see 1.

That's all for now. Kisses!

EDIT - 8/04/2026: Fixed slight Lore inconsistencies and fixed a spelling error.

(See the end of the work for more notes.)

Chapter 1: Canary, meet Coalmine.

Chapter Text

Chapter One; Canary, meet coalmine.

Somewhere in the Galaxy; aboard The Red Tear. Primarch Sanguinius’ chambers. 4AM - Terra Standard Time.

Sanguinius leans back in his chair, and thinks about his brothers.

More accurately, he thinks about their attitudes.

Dorn would not waste supplies; everything had a use, more than one in many cases, and his ships were always optimal because of it. He stocked carefully, stocked well, and always made sure that his sons did the same across his fleet.

Many saw it as being one of his ‘Dorn things’, Perturabo especially, but very few knew it was born of a deep seeded fear that was sown on his home planet; from his life before joining The Emperor.

“I have seen people starve because they didn’t prepare,” He said in the quiet peace of his office, “Starving, I’m sure you know brother, is agonising. It burns. If I can spare my sons that ache, I will. As long as I run the Imperial Fists, none will go hungry under my banner.”

Vulkan didn’t raise his voice unless in jest or in warning of danger. It was a skill all Primarch’s learned early; their ‘loud’ was enough to rupture human eardrums, even astartes airdrums, but Vulkan rarely lifted his voice an octave above a Primarch’s version of a ‘whisper’ but it still sounded booming to normal mortal’s ears.

“Yelling,” he said, voice calm, “doesn’t do anything when the world's falling apart. It inspires panic. We are The Emperor’s loyal servants, we are the shining beacon of light, we do not inspire panic; we inspire greatness, faith, safety, and we inspire trust. Yelling does not build trust.”

Leman’s door was always open, quite literally as he had the doors removed, rumor was, he had even removed them himself. He took his meetings in the war room, and his paperwork was done solely in his chambers, (when/if he did them, that is), leaving the office free for his sons to enter and exit as they pleased.

“A closed door, brother,” He said, downing his mug, “Is a closed welcome. On Fenris, the Chief’s doors are always open, they never close. To close them, is to turn your back on your people. I will never close the door on my sons; they are my sons, as simple as that.”

Magnus’ declared that no knowledge in his libraries were forbidden, he implored for his sons to ask him questions, and while sometimes his view was obscured by his own ego, he had his sons’ best interests at heart.

Lorgar let his sons organise their rooms as they saw fit, Alpharius did not care for gender or sex as a good spy is one who can play to the variables, Horus cut the hair of his closest sons himself - cradled their heads in his hands, Fulgrim let his sons read books and watch plays amongst themselves, the Khan permitted his sons to keep pets - birds mostly, and even Angron had rules he followed, even in his worst mental states. He never chained prisoners, and he never chained his sons; not to duty, not to the ground, not to obligation.

That too, Sanguinius knew, was borne from fear.

Primarch’s felt fear no matter what some might say, and even if they tried to deny it, many of their actions stemmed from it. Fear of failure, (Lorgar, Magnus, Perturabo), fear of being left behind, (Mortarion, Fulgrim), and fear of disappointment, (Dorn, Guilliman, Horus). It was an emotion they knew well, and was an emotion they all despised.

Sanguinius had asked his Father once, about why they felt fear. The Emperor hadn’t even lifted his head from His work as He said; “Fear is what defines us,” before beckoning His son to join him in overlooking his latest orders; a joint exercise between the Blood Angels and the Night Lords. Set to be performed within the upcoming month. It was meant to be seen as a brotherly alliance; a symbol of their unity for the Imperium.

But Sanguinius’ supposed the reason why he despised Konrad Curze so much at this moment all stemmed from that specific joint exercise.

For one, Konrad Curze had no lines. He had no boundaries. Nothing was off limits. His own rules didn’t apply to him and he broke the ones he had set often. Father had told him to pull his head in numerous times, but Konrad didn’t care, or perhaps more realistically, his mania kept his head in the sand.

Curze’s sons were no better. Most were cruel, shaped by the vicious vindictive insanity of their gene-father, backed into shadows with nowhere else to go, lest they be labelled traitors or deserters.

Sanguinius never realised how bad it all was until he had stepped foot onto that ship.

By Terra the anguish.

Commander Raldoron must have sensed his father’s agony and had discreetly placed his hand between his father’s wings, steadying him as they stepped forth into The Nightfall’s halls, walking towards the Bridge. His son’s warmth centered his mind enough to keep one foot in front of the other.

Sanguinius had forced himself to stand tall, to push through the Psychic onslaught and continue moving through the darkness towards the Bridge. His eyes lingering on the shadows, knowing what moved through them.

Sevatar greeted them on the bridge, saying that Curze couldn’t join them today, before he brought them to the training rooms; dark, miserable places, with little to no light. Sanguinius had an uncanny feeling that this whole exercise wasn’t going to end well, and he was correct even without his psychic power guiding his mind.

The two legions were like oil and water. His Blood Angels were bright in the darkness, while the Night Lord’s seemed to become it. His Angels fought not wanting to hurt their cousins permanently, while the Lord’s fought like they’re on the battlefield for real; live rounds and bone blades honed to points, slipped between armour joints and aiming for vital organs.

Sanguinius quietly called an end to the exercise just after the second day, when a Night Lord almost carved an already wounded Blood Angel’s head clean off despite said marine being out of the game. If it weren’t for Commander Raldoron’s excellent timing, who knows what could have happened.

”Thank you for your hospitality,” He said quietly to Sevatar, whose emotionless helmet gave nothing away, “But we need to join up with the Lunar Wolves soon for another joint exercise. Perhaps you could pass our condolences for our departure onto your father?”

Sevatar nodded slightly, but wasn’t able to tone down his arrogance as he drawled; “Yes, my lord.”

Thoroughly worried, Sanguinius called for his sons to return to The Red Tear and moved to follow them; wings twitching with alertness. His eyes narrowed as he scanned the darkened halls with more than simple wariness.

Suddenly, the actions of the Night Lord’s made perfect sense if this was how Curze had them trained.

He was so wrapped up in his own thoughts that he almost missed the small boy hidden up in the vents. If it weren’t for the psychic aura that resonated against his mental shields, Sanguinius would never have seen the boy; ripples in a pond.

Sanguinius’ footsteps hesitated, then stopped all together; his blue eyes locked on the boy’s own.

The child was small, skinny, with pale, corpse-like skin - as if he hadn’t seen the sun for years - and shockingly blue eyes, although they were offset by the deep bags underneath. His wavy black hair fell to just above his shoulders and was clearly unwashed. His clothes weren’t much better; his shirt looked more grey than white, with some spots cleaner than others, like someone had made an attempt but had given up. His face was no better; dirty with soot and ash.

The Primarch wasn’t sure what made him stop, but there was something about the boy that felt familiar. Not to mention his psychic aura felt… odd. It almost reminded him of Magnus’, but that wasn’t possible, because Magnus was a Primarch, and this boy was not.

”Little one?” Sanguinius had found himself asking, voice gentle as he could make it, stepping closer to the vent, which was about level with his eyeline. “What are you doing in the vents?”

The only response he got was the boy flinching back violently enough to slam his head on the metal, the bang resonating through the closed space, which was then followed by the sound of small steps rushing away from him, further into the ventilation shafts.

Sanguinius opened his mouth slightly, but no more words came out. He wasn’t even sure what he wanted to say. Beg the boy to come back? Apologise? Ask, again, what he was doing in the vents of The Nightfall? He closed his mouth and gazed into the gloom, but the boy was gone.

A little confused, the Primarch returned to his sons and entered The Red Tear; a reassuring sight after almost two straight days in utter darkness.

He made sure his injured sons were sent to the apothecary, and a runner had been sent to alert the command staff as to their latest rendezvous, (there wasn’t a meet-up organised between Sanguinius’ sons and Horus’, but now that he thought about it, perhaps a meeting between friendly faces would help his sons forget about their whole ordeal), before he stepped back into the hangar of his brother’s ship; Raldoron at his back.

Catching the attention of a, (conveniently available), nearby Nightlord Captain, Sanguinius asked him; “Are you aware of a child aboard your vessel?”

The Nightlord tipped his head slightly, as if considering his answer, before he calmly, but firmly, replied; “No, My Lord Primarch, there are no children aboard The Nightfall.”

Sanguinius gazed at The Nightlord, examining his helmet for a long moment; keeping his face carefully neutral. He lightly tapped on the Nightlord’s mental shields, but gleaned nothing from them, except a bad feeling.

”Very well, I apologise for wasting your time.” He murmured, turning away, letting his brow furrow as he stepped back aboard The Red Tear.

His bad feeling grew.

With the hangar doors shut behind him, Sanguinius bid Raldoron away, before returning to his chambers, where he now sat; pondering while gazing out across the stars, his dinner untouched on his desk. He was chewing his lower lip instead, a nervous habit he thought he got rid off, but apparently not.

The boy’s face flashed in his mind again; his small grimy face offset by his shocking blue eyes. Like diamonds in the rough.

Sighing through his nose, Sanguinius stood from his desk and walked to the viewing port, lip between his fangs still.

Shaking his head, Sanguinius forced himself to focus on the stars as they slowly began to blur. An alert sounded over the intercom system, informing all crew about their upcoming Warp jump, along with a countdown.

5…

Those eyes lingered in his thoughts.

4…

Why was he still thinking about the child?

3…

Was it because he’s a psychic? Clearly a powerful one at that? Albeit one who couldn’t control his gift? (Because he reminded him of Magnus?)

2…

By the throne the boy was so small.

1…

Closing his eyes, Sanguinius let the familiar sensation of Warp wash over him; the whole ship beginning to vibrate for a split second before the shields began to slowly push the powerful force of the in-between-realm away from the hull. Slowly, the ship began to settle, the metal began to breathe easy, and the rattling died down.

Opening his eyes again, Sanguinius gazed out across the endless expanse of virtual nothingness.

The Warp had a certain beauty to it, but only if you overlooked the dangers that lurked inside.

A small beep on his vox-caster drew Sanguinius’ thoughts from the swirl of colours, and he accepted the message from one of the Blood Angels who assisted in manning the bridge; “My lord Father, the Luna Wolves are ready to accept us.”

”Thank you, my son.”

With an uttered honorific, the Blood Angel signed off and Sanguinius dropped his vox-caster back onto his desk, and let his eyes slip closed again.

He needed to see Horus, perhaps a sane brother will help him clear his mind.

–✮⋆–

Somewhere dark.

’Boy. Told. Hide.’

’Sorry.’

’Sorry. Mean nothing.’

’Sorry.’

’Taught better.’

’Sorry.’

’Meaningless.’

’Sorry.’

–✮⋆–

Somewhere in the Galaxy; aboard The Vengeful Spirit. Hangar/loading bay. 5AM - Terra Standard Time.

”Brother!” Horus cheered, grinning wide with open arms, “To what do I owe this visit?”

Sanguinius smiled slightly and let his wings fold up against his back, wrapping his arms around his brother happily; Horus smelt of his usual aftershave, and the familiar smell made his shoulders un-tense; “We were just passing through and we thought we would stop by.”

Behind him, Raldoron greeted Ezekiel with a firm handshake and the two began to talk, shoulders pressed close as they spoke. Soon, Ezekiel was practically draped over Raldoron’s shoulders, chatting in his ear while keeping an eye on his fellow Luna Wolves, who were attempting to goad the Blood Angels into sparring with them right there in the hangar.

While the two marines weren’t close, there were few who matched them the way they could match each other, so it created a bizarre camaraderie between them, although they were usually at each other's throats.

”No armour today for you or your sons, brother?” Sanguinius asked Horus as they ducked into his office for a brief moment of peace between the Primarchs; somewhere where they’re able to speak freely.

”A servitor imploded in the cooling systems,” Horus explained, letting annoyance colour his tone as he rolled his broad shoulders. “The AC’s been down ever since.”

Sanguinius grimaced slightly, suddenly aware of the skin prickling heat, although it paled in comparison to Baal. “Do you know when it will be up again?”

His fellow Primate shook his head, “No,” He grumbled, “Half of my mortal crew have had fainting spells from the heat already. The Mechanicus are no help, constantly saying they’re ‘asking the machine spirit’, like it’s going to help with an imploded circuitry system.”

Blue eyes peering through vent grates.

Pushing those thoughts away, Sanguinius smiled at Horus, “Well, I bid you the best of luck, brother.”

Horus groaned, dragging a hand down his face, “Evil.” He grumbled, and Sanguinius found himself laughing, head tossed back.

There was something refreshing about speaking with Horus; like speaking with someone who understood him above being a Primarch. They truly were brothers in every sense of the word.

When Sanguinius lowered his head again, he found Horus gazing at him with a curious look.

”I haven’t heard you laugh in so long.”

That caught the angel off guard; his lips parted to speak but nothing came out, “Oh?”

Horus leaned back against his desk, the wood creaking slightly, “The last time was when we were at home, on Terra.”

Sanguinius remembered the last time he was on Terra with his brothers; a dinner amongst the Primarchs although several weren’t in attendance for one reason or another, Curze for his instability, (a running theme, it seemed), Alpharius as he was on a mission, and Mortarion, since he was in the middle of a siege on another planet outside Imperial space.

Their Father, like usual, could not, (or did not), attend, so it was just them inside Guilliman’s ship, docked in The Imperial landing yard, (it had the biggest meeting room and the finest food).

He remembered his legs tangled with Horus’ under the table, their shins knocking together each time one of them moved to take something off a plate, or to grab their glass. He remembered Vulkan laughing at the end of the table at something Dorn had said, and while the Praetorian remained neutral, his lips twitched slightly at the corners. He remembered how Leman was draped over The Khan’s shoulders, stealing things off his plate while his wolves begged Lion for scraps with their best impression of puppy dog eyes. He remembers how Magnus closed his book and began to interact with his brothers, his one lone eye gazing around the table with a similar emotion to what Sanguinius felt. He remembered how Guilliman passionately launched into an explanation of traditional Ultramar weaving patterns, which Fulgrim leaned over Ferrus to listen to, and while the Primarch of the Iron Hands grumbled, he moved his glass so his favourite brother wouldn’t knock it over his nice purple robes. He remembered how Corvus dozed off at some point, only waking when Lorgar discretely nudged him about the next course coming out.

He remembers laughing when Freki launched himself at an Ultramarine who had come in for a reason he can’t remember; laughing harder when Geri, upon Lion looking towards the commotion, snatched his steak off his plate.

Slowly, without him realising, a small smile stretched across Sanguinius’ lips at the memory, only for it to die.

When was the last time all his brothers were together in one room? Before Magnus and Leman’s animosity boiled over, before Angron’s nails began to tear his mind apart beyond repair, before Curze’s mental state deteriorated to what it was today?

When was the last time Guilliman, their youngest brother in all but age, smiled and spoke with such passion instead of exhaustion. When was the last time Ferrus and Fulgrim were together instead of being half way across the galaxy from one another? When was the last time Corvus attended their dinners? When was the last time Lion answered his letters?

When was the last time their Father was in the same room as all His sons? Not hidden behind golden doors? Untouchable. Unreachable. Uncaring.

His brothers were being torn apart by their duty, and despite knowing it was just that, their duty, Sanguinius found himself feeling oddly disheartened by it all.

He missed Guilliman’s smile, Dorn’s dry wit, The Khan’s gentle wisdom, his and Magnus’ talks. He missed his brothers; missed them like he would miss a lost limb.

”You’ve lost your spark, brother,” Horus continued, drawing Sanguinius back into the here and the now. He looked oddly melancholic, leaning back against his desk with his gaze heavy on Sanguinius’ shoulders.

Sanguinius thought back to Curze’s ship; thought back to those dark corridors and the Night Lords’s manic gazes.

”I-” Sanguinius trailed off, brow furrowing; “I never noticed.”

The office fell into silence for a brief moment until Horus, who always knew what to say, murmured; “How could you? None of us were around to remind you.”

’None of your brothers were close enough to tell you to smile. To help you to laugh. To tell jokes and share a table with you.’

”... I miss our brothers.”

’I’m lonely. I miss them. I want them back. I want them to be happy. I want. I want. I want.’

”I know.”

’I do too. I love you. I love them. I love. I love. I love.’

Taking a shuddering breath, Sanguinius briefly thought about meeting Him for the first time, (tears falling on red sands). How overjoyed he felt when he was told of his brothers; created in the same image. Brothers. His own family. A family that understood him in all ways. A family that would love him for everything he was; who would see him as an equal, not someone to worship.

”We should call another dinner,” Sanguinius ventured, looking at Horus’ face to see if he was onboard. “Just us brothers together.”

A small smile spread across Horus’ lips, “I would like that. But only if you can convince Fulgrim to share his wine.”

”Only if you can convince Leman to bring his Mjod.”

The small smile grew, and Horus was grinning now, “Deal.”

The fragile hope was disrupted by a knock at the office door, a reminder of their duties.

Horus straightened, reaching out to place a calloused hand on Sanguinius’ shoulder; the fur mantle shifting under his grip; “Don’t forget. Once everything settles down again, we’ll have another dinner.”

Sanguinius smiled gently, his lips curling up gently; “I’ll write a note. Now, let’s go watch my son’s grind yours into the dirt-”

–✮⋆–

Somewhere dark.

Firm hands cradle Boy’s face, lift it up so their (eyes) meet before pulling away.

’Look. Me. Talking.’

’Sorry.’

The hands shift back to his face, cradling his (head) now; large, overwhelming his (body).

’Father. Awake. Go.’

Boy shakes his head. ‘No.’

’Go.’

’Afraid.’

’Go.’

The hands move to his (back), push him towards the door gently, which (big brother) isn’t normally. His bare feet scuff along the (dirty) floor, knocking into the blankets; kick them away. He drags his feet.

The hall is dark, (scary), and he follows (big brother) to the darker hallways, then down into the darkest part of the (home). Time is an illusion.

Another (big brother) lies, bleeding, helmet gone, (jaw) torn off, by the door; slumped. Boy wants to check if he’s (alive), but (big brother) keeps him walking. The doors open. Boy hesitates at the (sight) but is nudged deeper inside.

Corpses hang from hooks, bones are scattered across the floor. Blood pools.

Tremors run from the floor up his (legs), from his feet. He knows there are more (big brothers), in the (big room) but (daddy) is probably angry with them, so he won’t get attached. Boy will be good.

He learned his (lesson).

(Big brother) hands vanish from his shoulders, and instead, (daddy) kneels down and grabs his arms; (strong), (hurts). Boy bites back a noise and lets (daddy) check him over for (hurts).

More tremors; talking. Someone is speaking.

Boy wants to go back to his (bed). Wants his blankets. And his book. And his (big brother).

(Daddy) is shaking. (Daddy) is (hurt), (angry), (hurt).

The hands go away now, and (big brother) rushes him from the room; a table shatters against the doors behind them, the tremors shake the doors and the walls. Shakes the floor.

Boy chokes on his (frustration).

The hands return; attached to (big brother); ‘Go. Sleep. Run.’

Boy obeys and breaks into a (sprint).

(Daddy) is (scary).

–✮⋆–

Somewhere in the Galaxy; aboard The Red Tear, currently locked in orbit with The Vengeful Spirit. Primarch Sanguinius’ chambers. 2AM - Terra Standard Time.

With a gasp, Sanguinius jolts awake; wings flaring wide.

A shattering glass pane. A broken Aquila. Fire, endless fire. The End and The Death.

Stumbling from his bed, he reaches for his desk and snatches a pen up, scrawling notes as fast as they enter his mind.

Bonds; broken. Raging death. The end draws near. Golden fire.

His fingers are trembling, but Sanguinius forces them to remain steady so his handwriting doesn’t look like mindless scribbles.

Darkness draws nearer. Howling wolves. A betrayal; or twelve. Crying. Someone holds his face. Blood. Blood. Madness. Father. Little brother. ‘Tool’, ‘Weapon’, ‘Number 13’.

Finally, the vision retreats and Sanguinius collapses, panting, into his chair; shoulders shaking with effort.

He drops his pen and cradles his head in his hands. A splitting headache rages behind his eyes. He feels a nosebleed coming on so he quickly snatches a handkerchief that Fulgrim gave to him a lifetime ago, and presses it to the flowing blood before it begins.

Once his breathing returns to normal, Sanguinius leans back and exhales shakily.

The vision made no sense; just bites of a future that could come to pass. But he knows it won’t because of the vision that came before, a vision of dying aboard… no. That vision has slipped too. It’s gone again.

This new vision takes its place.

This new vision is clear like crystal; clear like nothing before it ever was. This vision overrides everything he thought he knew. This vision is crisp at the edges, it makes sense; he can taste the falling ash on his tongue, and can feel the heat of the raging inferno’s against his palms.

His brothers will betray their Father. No- they might betray their father. They might cause the end of the Imperium.

What is it that Magnus used to say? Ah, ‘The future is always in motion; nothing is certain. Drawings in the sand.’

Sanguinius forces his eyes open and he looks around.

His reports meant for the Terra Archives are now covered in his hastily recorded notes, so he’ll need to rewrite both. His blankets are now sprawled across the floor, and his headache needs to be seen too at his earliest convenience.

But for the moment, he’s just going to sit, and wait, and breathe.

Another shaky exhale.

He can do all of that tomorrow; tonight, he just wants to sleep.