(a Kaiserreich x Fate: Grand Order one-shot.)

1939, a World on the Brink of Darkness
As Adolf Hitler rises to power, his twisted ideology begins to consume Germany and threaten the entire world. Otto von Bismarck II, great-great-grandson of the Iron Chancellor, senses something beyond mere politics at play. Rumors of dark rituals and occult forces surrounding the Nazi leadership spread like wildfire.

In his darkest hour, haunted by nightmares of ruin, Otto von Bismarck II encounters a force not of this world: Jeanne d'Arc Alter, a corrupted spirit born of vengeance and fire. Summoned into 20th-century Germany by mysterious powers, she appears as both salvation and temptation—an avenger who burns with hatred, yet carries a spark of reluctant justice.

A Meeting in the Ashes
Otto von Bismarck II had spent months trying to unravel the dark undercurrent surrounding Hitler's regime. The more he investigated, the more he became certain that Hitler was not just a man—he was something else. The Nazi leader's speeches carried an unnatural power that ensnared even the strongest minds. Whispers spoke of rituals deep in the Bavarian Alps, blood sacrifices, and otherworldly pacts.

One stormy night in 1939, while inspecting a cathedral turned Nazi headquarters, Otto was drawn by a burning light at the altar. The air shimmered, crackling with a presence not of this earth. From the flames emerged her.

Jeanne d'Arc Alter stood there, black armor reflecting the dying light. Her burning golden eyes fixed on Otto, and she smirked.

"You... are not what I expected. A mortal seeking to oppose the Devil's child?"

Otto, steady despite the supernatural encounter, responded with unshaken resolve. "If you know what he is, then you know I have no choice. The world hangs on the edge of hell."

Jeanne's smile wavered. For all her malice, she saw something rare in Otto—unyielding will, a man ready to sacrifice everything for his people. A silent moment passed before she tossed her black flag at his feet.

"Very well, Iron Prince. I will lend you my flames. But be warned—I serve no god, only the justice of fire. If you falter, I will burn you first."

Chapter 2: War of Faith and Despair
Their uneasy alliance began. Otto von Bismarck II worked to rally the military generals who despised Hitler's tyranny, while Jeanne d'Arc Alter served as both an ally and a reminder of the cost of failure. Her presence shook Otto's beliefs—she was no angel but something far darker, and yet she fought his fight.

Jeanne's hatred of the world matched the fire in Otto's heart. "You call him the Anti-Christ?" she sneered one night. "Men like him are born of humanity's sins. Your sins."

"And yet you stand beside me," Otto replied. "Perhaps you see the light that can still be saved."

She didn't answer, but Otto's words sparked something inside her. She watched him tirelessly fight against Hitler's regime, risking death, betrayal, and even his soul.

The Devil's Siege
By the winter of 1939, Hitler had sensed Otto's rebellion. The Gestapo hunted Otto and his allies, forcing them underground. Worse still, Hitler's occult experiments grew bolder. The Führer himself began to change—his presence warped reality, and his eyes gleamed with an unholy glow.

"He has transcended into something else," Jeanne warned. "If we don't stop him, the gates of hell will open. This world will burn."

Otto gathered his forces for a final battle in Berlin. Jeanne, standing at his side, finally revealed her own fears. "Do not think I fight for you, Otto von Bismarck. I fight to erase the corruption of men who think themselves gods."

"And yet," Otto murmured softly, "you still choose to save us."

Her expression wavered. She had seen his iron will, his refusal to kneel to despair, and somewhere in the darkness of her corrupted heart, she felt warmth—a fire unlike her own.

The Fall of the Beast
The climactic battle began as Otto and his forces stormed the Reich Chancellery, while Jeanne led a supernatural assault against Hitler's occult defenders. The city burned in the background as Jeanne unleashed her flames, carving a path to the Führer's chamber.

Inside, Hitler awaited them, transformed. His body glowed with dark energy, veins pulsing with infernal power. He laughed—a sound that shattered the walls.

"You are too late, Bismarck! The world will be mine!"

Otto stood firm. "Not while I draw breath, Devil."

As Hitler raised his hand to smite them, Jeanne leapt forward, her black flag shining brighter than ever before. "Your reign ends HERE!" she roared.

The fight was cataclysmic. Otto fought alongside her, fending off waves of occult energy with a pistol and sheer resolve. Finally, as Jeanne drove her burning flag into Hitler's chest, Otto fired the fatal shot. Hitler screamed, his body disintegrating into a dark, unearthly ash.

Flames of Redemption
In the aftermath, Otto von Bismarck II stood in the ruins of Berlin, watching the first light of dawn pierce the smoke-filled sky. The world had been spared the apocalypse, but at a great cost.

Beside him, Jeanne d'Arc Alter's black armor flickered. Her task complete, the fire within her began to wane. "It seems I am no longer needed."

Otto turned to her. "You saved us all. You have more than earned your peace."

She looked at him, her golden eyes softening for the first time. "It was you, Otto. You reminded me that even in the depths of despair, men can rise. You carry a flame even I could not extinguish."

As she began to fade, Otto reached for her, but her form slipped through his fingers like ash. "Farewell, Iron Prince."

Otto remained there, staring at the sky. He would carry her memory forever—the dark saint who fought beside him, the one who burned with both hatred and salvation.

His great-great-grandfather had forged Germany with iron and blood. Otto von Bismarck II had saved it with fire and faith.

And in the echoes of history, her name burned alongside his: Jeanne d'Arc Alter, the Avenger who chose to save mankind.