Deathly still on the bridge of his ship, he was surrounded by terminators and Astartes alike. Each of them burned with the power of the true gods.

Across the infinite plains of the Warp, he felt his father arrive with a pair of furious souls. Around him, tens of thousands in force, each food for his masters.

Horus licked his dry lips, sighing in anticipation as his father drew near, his ultimate demise awaiting. The burning pillar of golden warp-fire cleansed any touch of chaos that approached it.

The two of his brothers who'd arrived on the ship were separated from their lying father, and one of them he recognized with a pang in his heart. The only of his brothers he would truly, truly regret striking down.

Sanguinius burst into the bridge, the nearby Astartes killed the moment they attempted to move. Several terminators suffered the same fate before they recognized their father was not moving.

Deep in Sanguinius's burning soul, Horus could see regret. Fury, guilt, and vengeance all smoldered behind his searing gaze. Horus smiled. The angel did not.

"Brother." Horus said gently, smiling and swinging his arms wide. His mace lay motionless on his hip, he would not ruin his final chance to live forever over the Imperium due to a false notion of hostility. "Welcome."

Sanguinius was silent, Encarmine and Telesto both blazed with cerulean energy.

"I had hoped against all odds you would arrive first. For this very reason, actually."

"Do not play games with me, traitor." Sanguinius spat. "Say what you will, so that I may wipe your name from the stars." Horus sighed and stepped down from his pedestal.

Sanguinius was wounded, terribly so. Crimson ichor flowed from rapidly-healing wounds, his wings missing feathers in many places. Scorch marks adorned his armor, and his chest plate was marred with claw marks. He would have to visit terrible vengeance on Ka'bandha for that. Later.

"Please hear my words, brother. Our father, he would see the galaxy burn for his own hubris. Rather than admit his mistake, he wishes to let humanity die." Sanguinius again remained silent. But Horus saw surprise in his eyes. Was he getting through?

"Please, I offer you one last time. Join me, so that we might save humanity." The claws of his power armor melted away under Horus's psychic power. His flesh-and-blood hand exposed. "Please."

Sanguinius lowered his spear and blade, if only fractionally. The fury changed to sorrow.

"My brother is well and truly gone, it seems." The angelic man said. A single tear fell from his eyes. "The Horus I knew would have stopped at nothing to see our father succeed."

Telesto and Encarmine rose. Horus let his power claw slink back into place. He stepped away.

"I am sorry, Brother." Horus lamented.

The battle was hardly deserving of the title. Wounded and broken, as well as exhausted, Sanguinius stood no chance against Horus's might. Suffused with the power of the true gods, he smote Sanguinius's form against the stairs. The injured primarch raised his blade to stop the incoming mace.

The feeble defense barely stopped the weapon, but it was brushed aside by Horus's power claw. The very same claw swept across his face, slashing open his lips and sending blood flying. Horus's fury grew tenfold at his brother's unwillingness to see the truth. Why? Why would the noblest, the greatest of them all not see it? Why did he so blindly refuse to go against a cruel, evil man?

Why would he not accept the power of the true gods? His moment of internal fury was all that was needed for Sanguinius to rise up, his spear thrust straight towards Horus's own torso.

The moment the spear made contact, his mace came down on his brother's chest plate and crumpled it like tissue. His power claw seized Sanguinius's throat, and he was hoisted from the ground.

"Goodbye, brother." He snarled. The full power of his mind came down upon Sanguinius, and his brother screamed in agony.

Every misery the gods could divine was visited upon his soul. A million billion tortures falling upon his mind and body simultaneously. Piece by piece his mind was pulled apart from his body, and then cast away into the Warp. He tossed the lifeless body away, turning to see his accursed father enter the chamber. On each side over a dozen custodes in pitch black armor stood. Each wielding weapons from a forgotten era with destructive power beyond imagining.

"Father." He growled. "Look what you made me do." A gesture towards his brother's corpse drew the thing's gaze downward. He saw nothing behind the passionless eyes of his gene-sire. The emperor only looked back at Horus and furrowed his brow.

"This ends now."

"Indeed."

Almost too fast even for Horus, the Emperor moved. His sword came down in a vicious arc, stopping short against Horus's impervious mace.

The blade almost teleported to his side as the air burned with anger, golden light shining from his father's form. Horus replied in kind, black miasma rolling off of his body in waves. Their weapons shrieked with energy as they clashed, the room shaking with power.

Right as the Emperor almost gained the upper hand, Horus saw a flash of regret. It caused the killing strike to hesitate, and that was all he needed. His mace came up and smashed into his father's shoulder. His power claw ripped through his chest. His mace came down on his father's face.

Broken and wounded, his 'immortal' father looked up at him with hatred. Horus relished the emotion, drinking it in and smirking. And then, one of his father's billion sycophants stood between them. Barely large enough to be noticed. A single lasgun and paper armor.

And he thought to stand between Horus and humanity's doombringer. He rolled his eyes and eviscerated the fool, not even bothering to capture and feast on his soul. A worthless end for a worthless being. The chamber suddenly shook with power as the Emperor's full might rose up against him. Horus staggered backwards half a step as he recognized that he had not yet won.

But it was too late.

"HORUS LUPERCAL" the entire ship rattled under his father's mind. "YOU DIE"

He felt something leave him, a his body feeling weak and malnourished suddenly.

And he realized what he had wrought. A hundred thousand worlds devastated. Trillions of lives decimated. Sanguinius, broken and slain by his own hand.

He saw his father's mind rear up, and he closed his eyes. He deserved worse than death for what he had done to his father's dream. To humanity itself. The infinite power of an angry and betrayed father came down on him, and he felt his body and soul disintegrate to nothing.

"I am sorry."