Warhammer 40K: System Error, I Summoned the Arch-Traitor!

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After his meeting with the others concluded, Lion called Kullen away from the rest, just the two of them, in a small room off the main corridor.

The news Kullen carried was staggering. Even for a primarch, it required time to process, and even more time to verify.

Father and son. Sealed chamber. Sitting on the floor.

Kullen looked at the man across from him and felt a quiet surprise settle in his chest. Ten thousand years had done something to the Lion. Made him more candid, somehow. Less armored.

"Tell me about your time with Horus." Lion broke the silence first. His voice was low, but the enclosed space gave it an uncommon clarity. His emerald eyes caught the dim light and held it, steady and green and deep, like jade at the bottom of still water. "And that mortal friend of yours. From the beginning."

He paused.

"Leave nothing out."

"Yes, my lord."

Kullen didn't refuse. He drew a slow breath and reached into the deepest part of his memory, pulling up what had been buried there. He wasn't sure he was qualified to interpret what any of it meant. But this man was his Gene-Sire, and he was asking. That was enough.

He began at the underhive of Rysis. The encounter. The Emperor's dream-vision, and the mission that came with it. Then Cadia, and the fighting against Abaddon's Black Legion. Then the long road to Macragge, witnessing the awakening of the Lord of Ultramar, and finally the return to Terra for the Emperor's personal absolution.

Kullen laid it all out without embellishment and without evasion. His tone stayed flat and even throughout.

The words came out of him like a river running silent, surface unbroken, current deep, the kind of current that reshapes stone without announcing itself.

There was one exception.

When Kaelen came up, Kullen's phrasing went careful. Deliberately so. He told the Lion only that his mortal companion carried a personal guarantee from the Emperor of Mankind himself. Nothing more. No name explained. No details offered. He handled it like a wound he wasn't ready to show, or a secret that wasn't his to give.

Lion either didn't notice the gap, or chose not to press it. He gave a slight nod and filed the name away without comment.

Then he began to think.

His mind moved the way it always had, with the methodical precision of a hunting blade being drawn clean. He took everything Kullen had said and broke it apart, sorted it, laid the pieces end to end. Rysis. The Emperor's vision. Cadia. Macragge. Terra. Absolution. The words assembled into a web, and every thread in that web pointed the same direction: something enormous had been unfolding in his absence. Something far larger than he had anticipated.

A thought surfaced. He reached for the vox and called Zabriel.

The hatch slid open a few minutes later. A figure stepped through, Bevedan, the Librarian who had only recently found his way back to Lion's side.

"Bevedan." Lion's eyes moved to him. "Can you still intercept the whispers? The ones from the Empyrean — Chaos frequencies. I need to know the relationship between Horus and Abaddon."

"I can, my lord." Bevedan's voice came out rough, but the conviction behind it was solid.

He hadn't used his abilities in over a decade. The first moments were clumsy, like a hand reaching for a grip it no longer remembered. But then something clicked. His consciousness slipped free of his body and drifted outward, into the churning noise of the Empyrean, sifting through the chaos for the specific thread Lion needed.

When he opened his eyes again, they were dim with exhaustion. He looked at Lion and nodded.

"My lord. There is no mistake."

"Abaddon has announced Horus's return. He broadcast it across the full communication network of the Black Legion and every Chaos warband within reach. His tone was fury. Threats. And beneath that —" Bevedan paused, mouth tightening slightly. "Forgive the phrasing, but there was fear in it too. Abaddon and Lord Horus are not allies. They are not cautious rivals. They are enemies. This is not deception, not theater — it has been verified repeatedly across the whispers of the Empyrean."

Lion sat with that for a moment.

He had already heard, from Zabriel, the first of his sons he'd encountered, that Abaddon was the Imperium's most dangerous living enemy. That much was established.

But now Horus was back.

And so the question that followed was the one Lion actually cared about: how would Abaddon react to that? This man, this First Captain of the Luna Wolves, who had stood on the deck of the Vengeful Spirit and watched the Warmaster die, what did he still feel for the father who had made him?

Loyalty? Resentment?

Or something worse. That particular kind of obsession that lives in a son's chest when his father's shadow is too large to escape, the need to surpass, to eclipse, to finally be free of the name.

Lion's original theory had left room for sentiment. He'd half-expected there might be something between them still. Some remnant of their old bond, some mutual recognition that could complicate Horus's position and make his loyalties harder to read.

He had been wrong.

Two sources, entirely independent of each other. Kullen's direct experience. Bevedan's psychic intercept. They pointed to the same answer without hesitation: Horus and Abaddon were finished. Whatever had once existed between that father and son had been burned down to nothing. What remained was only opposition.

Abaddon's fury was real. Horus's severance was real.

Ten thousand years had put them at opposite ends of the galaxy, and when they looked across that distance at each other, there was nothing in their eyes but enmity.

Which meant something else followed, unavoidably.

Horus had no choice but to stand with the Imperium.

Not from feeling. Not from guilt. From the coldest kind of logic: his enemy was on one side, so he had to be on the other. That was it. That was the whole calculation.

And strangely, that cold simplicity made it more credible, not less. An oath sworn in tears was easy to doubt. A man with nowhere else to go was harder to argue with.

Even so, Lion didn't let his guard down.

Kullen had said the Emperor himself had absolved Horus. Bevedan's intercept corroborated the edges of that story. But Lion was a hunter, and hunters did not stake their lives on a single trail.

Horus had a record. He had personally set the galaxy on fire. That didn't vanish because circumstances had changed.

Lion would reserve his judgment. He would find the time to stand before the Golden Throne himself, face his father, and ask every question that needed asking. Until that day, his scrutiny would stay fixed on the Wolf of Lupercal, tracking that silhouette like prey that hadn't been confirmed dead.

As for Konrad Curze...

Lion's thoughts drifted to that name and lingered there for a moment.

Then, surprising even himself, he felt something ease in his chest. Something quiet and unexpected, like finding a window unlocked in a room you'd assumed was sealed.

Forget it.

Konrad had never really had anything to do with Chaos. Not truly. He wasn't a follower of the Gods. He wasn't a servant of the Warp. He was a madman, a man destroyed from the inside by prophetic visions he couldn't control and couldn't silence, thrashing alone in the dark for ten thousand years with nothing to show for it but scars.

Seeing him looking relaxed, even slightly, was worth something.

The greatest relief still belonged to Sanguinius, of course. And to that irritating... Roboute.

"What is Guilliman doing now?"

His attention returned to Kullen. When he said the name, his voice snapped back to its usual cool precision, but something underneath it, faint and almost invisible, was something close to care.

"The Lord Regent is leading a Great Crusade," Kullen answered. "The Indomitus Crusade — a relaunch of the campaign from ten thousand years ago. The scale is enormous. Almost the entire resource base of the Sanctum Imperium has been mobilized. Lord Guilliman departed Holy Terra and is pressing a full counteroffensive against the territories lost to Chaos and xenos."

"Lord Horus and Lord Konrad will depart for the Sanctum Imperium immediately after completing their meeting with you. Their itinerary is already set. No delays, no unnecessary stops. This war does not wait."

Kullen's voice shifted slightly, steadying into something more deliberate.

"As for the Lord Regent's overall strategic disposition, you will garrison the Dark Imperium alongside Lord Sanguinius. Full military authority over that region. All garrisons, all fleets, all fortress worlds. Direct command, no proxy."

The air in the room changed when those words landed. Not dramatically, but something in it lifted.

Lion's mood shifted with it. The corner of his mouth moved, barely, into something that wasn't quite a smile but was the closest thing to one that Lion's face usually managed.

Sanguinius. He would be fighting alongside Sanguinius, holding the darkest and most difficult stretch of Imperial space. Guilliman had looked at that assignment and decided Lion was the right man for it.

That wasn't just logistics. That was Guilliman saying: I still trust you at my back.

Maybe Roboute wasn't so insufferable after all.

The Lion let out a quiet, private sound that might have been amusement.

"And Horus? Guilliman didn't give him back the Warmaster title, did he?"

"No." Kullen shook his head. "Lord Horus refused it. More than refused, he said himself that he is no longer worthy of the title, and no longer needs it. He serves Lord Guilliman now as a military commander. Nothing more."

Who could have predicted that? The Master of the Luna Wolves, one of the greatest primarchs who ever lived, working under another primarch's authority.

The Lion was quiet for a moment, genuinely contemplating it.

"I have trouble imagining Horus accepting that willingly. With his pride..."

"Lord Horus has made his peace with what he is, my lord. He wants to be a weapon. He said he wants to learn to be like Lord Russ."

"He said that? Those exact words?"

Lion raised an eyebrow. The emotion in his voice was hard to place, not quite skepticism, but a careful, almost tentative need to be sure it was true.

"Yes. I watched him the entire journey. Every day of it. He wasn't performing, my lord." Kullen's voice stayed level, but the certainty in it was absolute. "The change was real. More real than repentance, because repentance comes apart, it bends back, it struggles, it fails and tries again. He didn't do any of that. It was as if he had released everything he used to be, and then picked up one single thing in its place. Something simple. Something he could hold."

A pause.

"In that way, he is like you. He has changed greatly."

"Lupercal." Lion said the name quietly, almost to himself. "Oh, Lupercal."

It came off his tongue with weight. Not hatred. Not anger. Something older than either of those, a long, complicated feeling that had been sitting in the dark for ten thousand years, slowly becoming something harder to name.

He leaned his head back against the cold wall and looked at nothing in particular.

"What am I even supposed to say to you?"

➤ Next: The Knight-Commander's Fanatical Dream

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