Fate's Slave - Shadow Slave X Honkai Star Rail

Far below the fractured battlefield, deep within the Underworld where the second Nightmare Gate pulsed like an open wound in reality, Aventurine moved with a very different kind of focus than the chaos above might have suggested.

While the plan had successfully forced two species of Nightmare Creatures into conflict, the result was not a perfect containment. There were always anomalies, creatures that refused to engage with their newfound enemies and instead turned their attention outward, drawn by instinct toward the far more desirable prey that humanity represented.

That was where Aventurine came in.

He hovered at a measured distance from the epicenter of the conflict, his glamorous armor reflecting the dim, corrupted glow of the Underworld in fractured glimmers. The enchantments woven into it hummed faintly, sustaining his position in the air as he observed the battlefield below with careful precision. His role was not to dominate the entire field, nor to waste energy in unnecessary displays of power. Instead, he watched for deviations, for moments where the delicate balance of violence threatened to tip in the wrong direction.

Above him, the collapsed opening between the Overworld and the Underworld continued to pour forth a steady stream of Corrupted creatures. Monsters fell first, then Demons, and occasionally Devils whose presence alone warped the space they occupied. They did not arrive in formation, nor with any cohesion, instead dropping chaotically into the territory below where the native Nightmare Creatures of the Underworld awaited.

The draconic entities born of True Darkness — Drakes, Wyverns, and Dragons — descended alongside them, their massive forms crashing into the ground with enough force to shake the surrounding terrain. Their roars echoed through the cavernous expanse, answered almost immediately by the howls of the wolves that inhabited the region around the second Nightmare Gate.

These wolves were no less dangerous.

Their bodies constantly expelled a faint, drifting cloud of spores that spread outward in a subtle yet pervasive mist. The effect of those spores was not immediately visible, but Aventurine had already witnessed what they did. Any creature caught within that haze began to falter, their movements growing erratic as their minds were flooded with a chaotic barrage of intrusive thoughts. It was not a simple confusion, nor a direct assault on their senses, but something deeper, a disruption of cognition that drove them into a frenzy where instinct overrode all else.

It made the battlefield below even more volatile.

Draconic claws tore through corrupted flesh while maddened wolves lunged without regard for their own safety, the two sides locked in a brutal exchange that consumed anything caught between them. For the most part, this worked in humanity’s favor. The creatures were too occupied with tearing each other apart to direct their attention elsewhere.

But not all of them.

Aventurine’s gaze sharpened as he noticed one of the Devils break away from the conflict, its massive form pushing through the chaos with deliberate intent. Unlike the others, it was not affected by the spores in any noticeable way, its movements controlled as it began to climb toward the edges of the battlefield, where the tunnels leading back toward human settlements lay.

That could not be allowed.

Aventurine moved.

He did not rush blindly, nor did he announce his approach. His figure shifted through the air with controlled acceleration, closing the distance in a smooth arc before descending upon the creature with precise timing. The Devil barely had time to react before his fist connected with its skull, the impact releasing a burst of force that shattered bone and sent its massive body crashing back into the ground.

He did not stop there.

Before it could recover, he followed through with a second strike, then a third, each blow delivered with calculated efficiency until the creature’s form collapsed entirely, its presence fading as it was reduced to nothing more than a broken husk.

Aventurine exhaled softly, his posture relaxing just slightly as he returned to his previous position.

"Stay in your lane."

Below, the war continued unabated.

***

Elsewhere in the Underworld, the situation was far less controlled.

Clara moved through the streets of Boulder Town with measured steps, her expression calm despite the tension that lingered in the air. The automatons under her command maintained a tight perimeter around her, their mechanical forms positioned strategically to respond to any threat that might emerge.

Yet there was nothing.

No sign of the red blur that had escaped from the Nightmare Gate.

She paused briefly, her gaze sweeping across the empty streets as she processed the absence of any visible disturbance. The reports she had received were not exaggerated. The speed at which that creature had eliminated multiple units in mere seconds was beyond anything she could ignore, and yet now, there was no trace of it.

Her fingers tightened slightly at her sides.

"Where did you go...?"

***

Outside of Belobog, the battlefield had fractured into multiple fronts, each carrying its own weight of danger and urgency.

From her position, Bronya watched both.

Her focus shifted constantly, her abilities extending outward as she reinforced those still fighting, her influence weaving through the battlefield in subtle yet vital ways. The strain of maintaining that level of support was evident in the tension that lined her expression, though she did not allow it to falter.

Her gaze lingered longest on Sunny.

And what she saw unsettled her.

He was not fighting.

Instead of meeting Cocolia head-on, instead of continuing the clash that had already pushed him to his limits, he was retreating. His movements were sharp and deliberate, his path cutting away from the primary battlefield as he drew Cocolia’s attention with him.

He was running.

Not out of fear.

But with purpose.

Bronya’s brow furrowed slightly as she processed the implication, her understanding catching up quickly enough to realize what he was doing. He was creating distance, pulling Cocolia away from the others, isolating her in a way that would prevent her from interfering elsewhere.

It was a dangerous gamble.

And one that relied on someone else surviving in the meantime.

***

Seele did not allow herself the luxury of hesitation.

Despite the turmoil that churned within her, despite the grief that threatened to rise with every glance at the figure pursuing her, she forced it down, burying it beneath the immediate necessity of survival. There was no space for doubt in a fight like this, no room for the kind of hesitation that would cost lives.

She moved.

Her body blurred through space as she warped forward, reappearing just ahead of Veliona’s outstretched hand. The attack passed through the space she had occupied a fraction of a second earlier, the air itself distorting slightly from the force behind it.

Veliona laughed.

The sound was sharp, erratic, laced with a manic energy that carried none of the restraint she had once possessed. Her movements followed the same pattern, unpredictable and relentless as she warped again, closing the distance with alarming speed.

Seele twisted, her scythe sweeping outward in a defensive arc that kept just enough space between them to prevent direct contact.

She could not let Veliona touch it.

The moment those fingers traced the lines of Death along her weapon, it would be destroyed, erased in a way that her current abilities could not recover from. That limitation forced her to fight differently, to rely on movement and spacing rather than direct confrontation.

Their Abilities, once shared, now stood in stark contrast.

Separated, they had gained more power, but at the cost of synergy.

Veliona’s Ascended Ability granted her an instinctive awareness of Death, allowing her to avoid it with unnatural precision. Seele’s own granted her an enhanced healing factor, a resilience that allowed her to recover from injuries that would have ended most fights.

But against Veliona...

That healing meant nothing.

Veliona lunged again, her fingers slicing through the air as she aimed for Seele’s torso, her movements fluid despite their chaotic nature. Seele warped away, reappearing behind her as she swung her scythe in a counterattack aimed at her back.

Veliona was already gone.

The two of them moved like streaks of light across the battlefield, their positions shifting constantly as the distance between them collapsed and expanded in rapid succession. There was no direct clash, no moment where their weapons met in a prolonged exchange.

***

Farther away, Sunny felt the shift before he saw it.

The shadows around him reacted first, stretching and warping in response to a sudden, overwhelming light source. His instincts took over immediately, his body moving before his mind could fully process the threat.

He rolled.

The moment he moved, the world split.

A golden beam tore through the space he had just occupied from the tip of Cocolia’s spear, its path extending far beyond him as it carved through the landscape with terrifying ease. The ground shattered in its wake, the force of the attack carrying forward until it reached the distant mountain range.

It cut through it.

The mountains did not resist.

Stone, ice, and earth were cleaved apart as if they held no substance at all, the beam continuing onward until it finally dissipated in the far distance, leaving behind a scar that would not fade any time soon.

Sunny stared for a fraction of a second, his expression caught between disbelief and grim understanding.

Then he turned and ran.

’Just... keep running!’

There was no other option.

Cocolia’s attention remained locked onto him, her movements following his with relentless focus as she prepared to strike again. The influence of Hail Sorrow ensured that she would not divert her attention, that her intent would remain fixed solely on ending him.

That was exactly what he needed.