Caelan could have chosen a gentler approach.
He could have started by telling Mortarion that there are good and bad people in the world, and that psykers, too, can be good or evil.
Just as he once taught Angron: "Law bears no morality of its own. In righteous hands it becomes justice; in wicked hands, corruption."
Given time, Caelan believed Mortarion would understand. But he chose not to hold anything back.
Mortarion was no longer a child. He had read many books and understood many truths.
Even though he still sought light in the darkness, he had a stubborn side.
If Caelan only handed him fragments of truth, Mortarion would surely believe he was weaving lies out of carefully chosen facts.
That's what the Emperor had done. He was more honest with Mortarion than with any other Primarch, even revealing his grand plan: to eliminate humanity's dependence on psykers and warp travel.
Everything the Emperor said was true, but selectively so.
If humanity could control the Webway, it could abandon warp travel.
If humanity ascended into a psychic species, with every person a psyker, then dependence wouldn't matter.
Even the historic Council of Nikaea had been discussed with Mortarion beforehand.
The Emperor had chosen Mortarion to preside over the council. From the beginning, they knew it would become a trial for Magnus and the Thousand Sons.
No other Primarch, not even Horus, had received such an honor.
And yet Mortarion still betrayed him, because he sensed the Emperor was hiding something.
Even if every word was true, the moment Mortarion detected hesitation or omission, he would spiral into paranoia.
To him, every noble truth became a carefully crafted lie.
So Caelan chose a dangerous method of enlightenment, not peeling back layers of truth, but handing Mortarion the burning core and letting it cool into understanding.
"If truth were easily accepted, it wouldn't be worthy of the name."
"No matter what the truth is, I'll judge it myself," Mortarion rasped. "The gods want me. What about you? What do you want from me?"
"My only wish," Caelan said softly, "is to tell you the truth and to teach you. Nothing more."
"You ask for nothing else?"
"Nothing else."
"I don't believe you!"
Mortarion stepped forward, his massive frame casting a shadow like a mountain, drowning Caelan in darkness.
He glared at the stranger, breath rasping and heavy.
He couldn't believe Caelan wanted nothing. He couldn't believe truth came without cost. He couldn't believe the warmth given to him was anything but charity.
Caelan met his eyes. Mortarion stared for a long time and saw only clarity, no fear, no calculation, no evasion. Just a pure, tranquil sincerity.
"Keep talking," Mortarion growled, his voice low and thunderous.
Caelan lowered his head, frowning silently.
"You're hesitating."
'See?' Mortarion thought bitterly. 'The stranger is weaving lies.'
Caelan raised his face from the shadows. "I'm just deciding where to begin."
"Start with the gods. Tell me, who are they?"
"There are four major Chaos Gods in the warp: Tzeentch, Khorne, Nurgle, and Slaanesh. Each of them wants you."
"Slaanesh is the youngest. The warp storms that ravaged the galaxy during the Age of Strife were the birth throes of its coming. Only when Slaanesh emerged did those storms finally calm."
"And the one who turned Barbarus into this cursed land… was Nurgle."
Lies! Don't listen to him!
Mortarion asked coldly, "What kind of god is it?"
"Nurgle embodies decay, disease, death, and rebirth," said Caelan. "He loves life, but he loves the rot and plague of life more than life itself."
"Except for Slaanesh, the other three gods likely emerged tens of millions of years ago during the War in Heaven."
Don't believe him! Your father loves you! This stranger is lying!
"They feed on mortal emotions and were born from them. Their essence is the accumulation, fermentation, and elevation of countless mortal feelings in the warp, until they became terrifying entities."
I love you! My child, I love you!
"Other entities can be born in the warp, but the four gods devour them before they can fully form, using them to feed their eternal hunger. Even those that escape must flee in terror."
I'll show you, child, he doesn't love you!
"Worse still, even the birth of other entities may be part of the Chaos gods' schemes."
Lies! All lies! He's weaving lies from truth!
"I'm telling you what I know. It may not be complete, but it's accurate."
Caelan looked at Mortarion's pale face. "Are you okay? You look terrible."
He doesn't love you! He loves your brothers! Only I love you, come to me!
Mortarion's face twisted. He clenched his eyes shut, as if trying to shut out the world.
Inside his skull, voices echoed, gentle persuasion like dull blades slicing flesh, a father's grief like winter wind, siblings' calls laced with sobs, and laughing sprites bombarding his mind like spam.
Bang!
Mortarion collapsed to his knees, his gaunt body curling like a broken scythe.
"Help… help me…"
He tried to cry out, like a helpless child calling for his father.
But the pain clamped his throat like iron, leaving only silent gasps.
He felt the world peeling away, casting him into an endless void.
Slimy, sticky hands wrapped around his limbs. Inhuman things laughed sharply, dragging him inch by inch into the abyss.
Then, silence.
All noise receded like a tide, leaving only emptiness.
And then, someone embraced him.
The arms were slender but firm, radiating impossible warmth.
His forehead rested against a chest, hearing steady heartbeats, anchors in the dark.
He had never been held like this.
No calculation. No pity. No words.
Just pure, warm… redemption.
"It's okay now," Caelan whispered gently, like soothing a frightened child. "I can feel Chaos whispering in your ear. Your brother Lorgar went through the same."
At the mention of Lorgar, Mortarion's face twitched, like ripples on a still lake.
"Continue," he rasped. "Tell me everything."
Caelan's voice was soft. "I will. But you need rest."
"I'm fine. Tell me the truth. Please…"
His throat bobbed violently. His voice exploded like thunder, then faded into trembling breath.
His fingers clenched white, his voice twisted into humble pleading, like a drowning man grasping his last straw.
Caelan's voice turned stern. "I do spoil children. But you're an adult now. My indulgence has limits."
Why?
A burning resentment surged in Mortarion's chest.
Why was indulgence limited only for him?
Why was he the only one expected to be grown?
If he was an adult, then what about his spoiled brothers? Could they remain children forever?
"You're the one who came late!" he sobbed, roaring like a wounded beast.
He saw it!
The father's canvas unfolded before him, Caelan laughing with his brothers, their warmth, their unspoken bond, their closeness. They were like a real family.
He saw it all!
Caelan gave them all his love. And what did he get?
Only endless pain and torment.
Even the scraps of affection he received were rationed.
"It's my fault," Caelan said softly, wiping tears from Mortarion's eyes. "I came too late. But I'll spend the rest of my life making up for it. Now close your eyes. When you wake, my past, present, and future are yours to question."
Mortarion clutched Caelan's collar. "Don't leave. Don't disappear. You haven't told me the truth. I'm not grown… I haven't learned to live alone…"
Caelan's fingers brushed through his damp hair, like smoothing the feathers of a frightened bird.
"I see it now," Caelan chuckled. "You're just a big boy who cries into his father's shirt. I'm not going anywhere until you grow up. I promise."
Mortarion locked eyes with Caelan, trying to pierce his soul, and found no trace of deceit.
He knew Caelan wouldn't lie. But only by staring into his eyes could his restless heart calm.
His grip loosened slightly, but he still clung to the fabric, his last lifeline.
"Read my diary. Don't go. Please… Father…"
But exhaustion finally overcame him. His eyelids fell like iron gates.
Mortarion had just awoken from a deep, dreamless sleep, one unlike any he'd ever known. Yet even in that stillness, a phantom anxiety clung to him like mist. He jolted upright, eyes wide, searching.
"Caelan!"
"I'm here."
Caelan's face came into focus, his eyes filled with concern, glowing softly in the dim light. Mortarion's chest heaved like a storm-tossed sea, but slowly, his muscles relaxed. Without thinking, he lay back down, his head resting on Caelan's lap.
Both of them froze.
Caelan broke the silence first. "My legs are numb. Mind if I stand for a bit?"
"Sorry."
Mortarion shot upright, nearly knocking over the stack of books beside him. Caelan leaned against the stone wall, stretching his legs with difficulty. He stumbled slightly.
Mortarion's arm shot out like lightning, steadying Caelan's shoulder.
"Why?" Mortarion asked quietly.
"You mean the lap pillow? Because you wouldn't let go of my collar."
"You're blaming me?" Mortarion snapped, surprised even by his own words. That wasn't what he meant to ask. But something deeper, something bitter, was stirring inside him.
"How could I blame you?" Caelan's voice was gentle. "No father blames his child. Especially not a frightened one."
"I wasn't afraid!"
Mortarion's voice rose sharply. Caelan's words felt like a humiliation.
Silence crept in. Mortarion hated silence.
He forced out the words: "The truth. You haven't told me yet."
"Alright," Caelan nodded. "What do you want to know?"
"Anything."
The moment the words left his mouth, Mortarion regretted them. He still craved truth, his obsession ran deep. But now, something else stirred in his heart: a fear of reaching the end.
It was absurd. Their journey had only just begun.
As Mortarion stared into Caelan's eyes, seeing his own reflection flickering in those pupils, he wished time would freeze.
Let this conversation stretch into eternity. Let every answer birth new questions. Let truth remain forever suspended in ambiguity.
But he knew, Caelan would eventually leave. He had other brothers scattered across the galaxy, all yearning for redemption.
Mortarion was unlucky. Caelan had come too late. His childish brothers had greedily stolen too much time.
The scars left by his foster father still ached. He didn't want his brothers to suffer the same fate.
"I don't know where to begin," Caelan admitted. This was unlike any lesson he'd ever given. His thoughts churned, searching for a starting point.
Just then, a knock shattered the stillness.
Mortarion instinctively stepped in front of Caelan, shielding him. "Did anyone come while I was asleep?"
"No."
Mortarion's voice dropped to a wary growl. "My foster father is coming. We have to escape. Stay behind me."
Caelan nodded. "I'll follow your lead."
Mortarion opened the door. The gatekeeper slave's cloudy eyes locked onto him instantly.
"What is it?" Mortarion asked coldly.
The slave lowered its head in fear. "Mealtime…"
Mortarion lowered his gaze too. These puppets were sent by his foster father to monitor him.
They had once been living beings. Now they were stitched-together monstrosities, animated by warp sorcery.
They couldn't lie. Their minds were too broken.
So yes, it was mealtime. That meant his foster father hadn't discovered Caelan yet.
But he couldn't take chances.
Without warning, Mortarion kicked the twisted creature hard.
The stitching tore instantly. Rotten flesh and shattered bone scattered like a broken doll.
The corpse flew through the air, slammed into the stone wall, and slid down like sludge.
Before the other slaves could react, Mortarion was already moving.
Though barely over two meters tall, still bearing the outline of youth, he was a Primarch.
His speed was inhuman. Every strike landed precisely at joints and tendons, dismantling the abominations like toys.
Bones snapped like branches in a storm. Rotten flesh splattered. Stitching burst. The grotesque constructs fell apart under his hands, like puppets torn apart by a child.
By the time Caelan stepped into the corridor, it was littered with mangled remains. The stench of decay flooded his senses.
Seeing Caelan wrinkle his nose, Mortarion offered a dry explanation: "Slitting their throats doesn't kill them."
.....
If you enjoy the story, my p@treon is 30 chapters ahead.
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