Fate's Slave - Shadow Slave X Honkai Star Rail

Sunny did not linger on the thought for long.

There was a brief, almost ceremonial finality to the next movement. He stepped forward, planted his shoulder into the automaton’s chest one last time, and drove it cleanly across the chalk boundary with a smooth, practiced motion that carried none of the earlier trial-and-error. The machine stumbled, metal feet scraping against the ground before stabilizing outside the ring.

He exhaled, straightening as the Mantle of the Underworld shifted subtly across his frame, its onyx surface catching the dim Underworld light like polished stone.

Then, without ceremony, he smiled.

"Thanks, Clara. That helped a lot."

Before she could respond, before the confusion in her expression could settle into a question, his form blurred.

Shadow swallowed him whole.

*** 𝐟𝕣𝕖𝐞𝐰𝕖𝚋𝐧𝗼𝚟𝐞𝕝.𝗰𝐨𝐦

He reappeared deeper within the Underworld, far removed from the relative order of the settlement.

The building he chose had long since been abandoned, its structure partially collapsed and leaning at an angle that suggested it had given up resisting gravity. Rusted metal beams jutted from fractured concrete, and the interior was littered with debris that had not been disturbed in years. Shadows pooled thickly in every corner, undisturbed by movement or purpose, forming a quiet, oppressive stillness that most people would have found suffocating.

Sunny found it comforting.

He stepped forward from the darkness as though it had simply decided to release him, his boots crunching softly against grit and broken fragments. The silence pressed in around him, not empty but dense, as if it carried the weight of everything that had once occupied the space.

He let out a slow breath and leaned back against a cracked wall, tilting his head slightly as he focused inward. The familiar lattice of runes unfolded before his perception, precise and unyielding as ever, revealing the state of his Memory.

Memory: [Mantle of the Underworld].

Memory Rank: Ascended.

Memory Tier: VII.

His gaze immediately shifted to the enchantment he had spent years building toward.

[Prince of the Underworld]

Enchantment Description: "This armor grows stronger according to the amount of opponents its wielder defeats."

Vanquished Foes: [6000/6000]

He stared at the number in silence, letting it settle.

Six thousand.

The figure carried weight not because of what it represented numerically, but because of what it implied. Time, effort, persistence, and a refusal to abandon a goal that had long since ceased to be practical. He could not remember the exact moment he had obtained the Mantle, but he knew his general history. The Forgotten Shore. Back when he had been a Sleeper, fragile and inexperienced, forced to rely on whatever scraps of power he could gather.

That had been over half a decade ago.

He huffed quietly, a faint trace of disbelief slipping through his otherwise controlled demeanor.

’Six thousand enemies, and nearly a third of them came from one poor robot.’

There was no guilt in his voice, only mild amusement. If the system allowed it, then it was a valid method. The Nightmare Spell had never cared about fairness, only results.

Pushing himself off the wall, Sunny straightened and examined the rest of the runes. The Memory had advanced, as expected. Its Rank remained Ascended, but its Tier had increased.

Memory Tier: VII.

The improvement was noticeable, but not dramatic.

He clicked his tongue softly, neither satisfied nor disappointed, simply acknowledging the outcome. He had not expected a miracle, but he had perhaps anticipated something more... significant.

His attention shifted to the enchantments.

Memory Enchantments: [Living Stone], [Feather of Truth], [Stalwart], [Underworld Armament], [Prince of the Underworld].

All unchanged.

Predictable.

Then his gaze paused.

At the end of the list, something new had appeared.

[Soulbound Relic]

Sunny’s expression sharpened slightly. The absence of a description was immediately concerning. The Nightmare Spell was rarely vague without reason, and when it chose to withhold information, it was usually because the decision itself mattered more than the explanation.

He focused on the new enchantment, and a prompt appeared without delay.

[Bind the relic?]

He exhaled slowly, folding his arms as he studied the simple, unhelpful question.

There were no details, no warnings, no indication of what binding the relic would actually entail. It was a binary choice presented without context, which was precisely the kind of situation the Nightmare Spell seemed to enjoy.

Sunny’s gaze darkened slightly as he considered it.

The Mantle of the Underworld had not been created by a benevolent force. It was tied to Nether, the Daemon of Choice, an entity that existed somewhere between myth and threat. Even if Nether was dead, that did not guarantee safety. If anything, it made the situation more uncertain. Dead things had a tendency to linger in ways that defied logic, especially when they had once operated on a conceptual level.

His mind drifted briefly to his Innate Ability.

[Shadow Bond].

A so-called blessing that had stripped him of his freedom, binding him in ways that no ordinary chain could replicate. The Nightmare Spell had deemed it beneficial, despite its cost. That alone was enough to make him question any reward it offered.

Still, the fact remained that he had spent years building toward this moment. Walking away now, simply because of uncertainty, felt... wasteful.

Sunny tilted his head back slightly, staring at the cracked ceiling above him.

’There’s no point in stopping here.’

The words were quiet, but resolute.

He lowered his gaze back to the prompt.

"Yes."

For a brief moment, nothing happened. There was no immediate reaction, no visible change in the runes or his surroundings. The silence stretched just long enough to become noticeable, and Sunny frowned slightly, a flicker of suspicion rising.

Then the Spell spoke.

[Your Memory has been destroyed.]

Sunny froze, his expression going blank in a way that suggested his brain had momentarily failed to process the information.

’...What?’

The thought came out slowly, flat with disbelief.

He stared at the runes again, but there was no mistake. The Mantle was gone. Not hidden, not altered, not sealed away. Destroyed.

A hollow sensation settled in his chest as the reality of it sank in.

"That was my armor..."

His voice rose slightly, incredulity bleeding through.

"My very distinctive, very useful, very intimidating armor!"

He ran a hand through his hair, exhaling sharply as frustration spiked.

"How am I supposed to look threatening now?! Do you have any idea how much presence that thing carried?!"

The silence that followed was, as always, entirely unhelpful.

For a brief moment, Sunny genuinely questioned whether he had just made an irreversible mistake.

Then the Spell spoke again.

[You have received an Attribute.]

The frustration stalled, replaced by cautious curiosity.

"...An Attribute?"

That was new.

Sunny focused inward again, opening his list of Attributes with deliberate care.

Attributes: [Fated], [Essence of Divinity], [Master of Shadows], [Breach of Styx], [Deviant], [The War], [Blood Weave], [Bone Weave]...

Sunny noticed that the [Pathstrider] Attribute was gone and replaced by a new Attribute, but his gaze moved down the list until it reached the end.

There, a new entry had appeared.

[Marble Shell].