The Greatest Assassin Gets Reincarnated in Tensura

Arion's presence in the Cardinal World had grown immeasurably powerful. He had unlocked unimaginable potential in the last few years, not only mastering the art of stealth and manipulation but also increasing his own power to the point where space itself seemed to bend at his will. His newfound strength gave him the freedom to traverse worlds effortlessly, so when he decided that the Underworld would be his next stop, there was no hesitation.

His mind raced as he stepped into the blackened rift between realms. The very air tasted of sulfur and decay as the dim light of the Underworld greeted him. The red skies, swirling with dark clouds of ash, served as a constant reminder that this was a land not governed by mere mortals, but by souls and the corrupt forces of chaos.

The Underworld was the perfect place to recruit soldiers. The demons here were strong, primal, and would respect nothing less than absolute power. Strength was their currency, their law, their essence. Arion could already feel the energy of the land, the intense demonic auras that lingered like suffocating mists in every corner.

Arion didn't waste any time. He scanned the area, reaching out with his mind, filtering through the dark, twisted energy that pervaded the underworld. He knew that Noir, one of the most powerful demons, would be his best lead. Noir was known for his cunning, power, and deep understanding of the underworld, and Arion had spent enough time with him to understand that Noir would be a perfect candidate for the kind of army Arion intended to build.

Arion's steps were silent, almost as if he wasn't even there. He moved with purpose, honing his senses to track Noir's precise location. It didn't take long before he pinpointed the exact spot: a vast, hellish citadel, surrounded by pools of fire and swirling shadows, where Noir was most likely plotting or contemplating his next move. Arion grinned as he prepared to make his entrance.

With a thought, Arion vanished—not a trace left behind, not even a whisper in the air. His mastery of presence erasure meant that he could now slip through the fabric of reality without a single being noticing.

Inside Noir's domain, the atmosphere was thick with the scent of brimstone. Noir, standing in front of a massive, shadowy throne, was lost in thought, unaware of Arion's presence. His mind was wrapped in schemes and plans, his sharp eyes gleaming red with the weight of his responsibilities.

Then, suddenly, Arion was right behind him—as if he had materialized out of thin air.

Noir's senses, honed over eons of existence, did not pick up even the faintest disturbance in the air. He was caught off guard. His body reacted instinctively, and with a flash of crimson light, Noir's form flared with demonic energy. He twisted around in an instant, the very essence of his power surging to meet a possible threat.

But as Noir spun, there was no immediate threat—instead, he found himself face-to-face with the familiar, smirking figure of Arion. His gaze sharpened, the demonic lord's eyes narrowing, as his mind raced to process what had just happened.

"You've grown rusty, Noir," Arion's voice rang in the silent citadel. It was almost mocking, a hint of playful challenge in his tone.

Noir froze for a fraction of a second, disbelief flashing in his eyes. "What...?" he muttered under his breath, the shock and fury in his gaze apparent.

Then, his expression shifted into something darker. With a snap of his fingers, the shadows around them roiled, and Noir's body glowed with a dark aura, ready to strike. But his sharp senses suddenly recognized the voice—it was Arion. The shock quickly turned into annoyed amusement.

"You… How the hell did you…?!" Noir hissed, his voice laced with a dangerous edge. "You always were full of tricks." He lowered his guard but not his vigilance, his red eyes still burning with suspicion and something else—excitement.

"I am Arion now. That is my name," Arion replied coolly.

Noir's eyes widened slightly as the name clicked in his mind. He thought for a moment, memories flashing before him. Then, his lips curled upward in realization.

"Wait, I know that name. The VOTW. You're Arion... the one who evolved into a Demon Lord."

Arion nodded, his eyes steady. "Yes, that's me. I've surpassed what I once was, Noir."

Noir leaned forward slightly, his dark eyes gleaming with interest.

"Interesting. So, you were able to evolve—to transcend the limits that even I could not. You've ascended beyond the primordial demons, huh? Impressive." His tone had a strange mix of curiosity and respect.

Arion's form exuded a deep confidence. He was not the same being that Noir had once known. His strength wasn't just physical—it had become an all-encompassing force that could not be easily quantified. Noir knew better than to question the full scope of Arion's power.

Arion's expression was unreadable, but inside, he could feel Noir's curiosity and respect growing. It was time to make the next move.

"I've come here because I want to recruit demons, Noir. Strong demons. I know you'll understand this. But I want you to join me, to lead an army. One that will control everything from the shadows," Arion said, his voice low but commanding.

Noir looked at him, an amused glint dancing in his blood-red eyes.

"Demons only respect power, Arion," Noir said, crossing his arms. "I can already sense that you're stronger than most. But before I pledge myself to you, I need to see it firsthand. I need to know you can handle yourself. After all, I don't follow anyone who is weaker than me."

Arion smirked, unfazed by Noir's challenge. He was well aware that demons only followed the strongest. It was in their nature. And even though he had already ascended to demon lord status, he understood Noir's need for proof.

"Sure. No problem," Arion said casually, as if Noir's challenge didn't faze him at all.

Without another word, Arion snapped his fingers, and instantly the two were no longer standing amidst the fires of Hell. They were somewhere else entirely—in a dimension that bent and twisted in alien ways, filled with shifting landscapes, swirling shadows, and limitless space. It was a realm of pure chaos, created just for this battle.

Arion gestured toward the space around them.

"Here, Noir. You can go all out."

Noir didn't need any further invitation. His eyes glowed with demonic power, and with a roar, he released his full energy. The world seemed to quake as his demonic aura tore through the air, his flames of annihilation blazing in every direction. The ground beneath them cracked, sending fissures through the very fabric of reality. Noir was a force of destruction, a being who had ruled for eons and carved his name into the Underworld's very bones.

"Let's see if you can keep up, Arion!" Noir roared, his body becoming a colossal being of destruction, surrounded by chaos.

But Arion was unfazed. His form seemed to blur, and in a flash, he disappeared, only to reappear directly in front of Noir. The demon had barely registered the movement before Arion's fist crashed into his chest, sending him flying through the air like a ragdoll.

Noir struggled to maintain his balance, his dark powers surging once again. But Arion was already there—each strike, each movement was too fast, too powerful. Noir's attacks barely landed, and even when they did, Arion seemed to brush them off like mere inconveniences.

In the span of mere seconds, Noir found himself on the ground, unable to comprehend what had happened. His body was bruised, battered, and his once untouchable aura now seemed weak in comparison to Arion's overwhelming power.

"This... this isn't possible..." Noir muttered under his breath, his usual composure completely shattered. He couldn't believe it—Arion had utterly crushed him in a matter of moments.

Arion snapped his fingers again, and just like that, they were back in Hell, standing in Noir's domain once more. The surrounding fires flickered, as though acknowledging the shift in power. Noir stood still for a moment, panting, his eyes wide with both disbelief and a grudging admiration.

"Alright, you convinced me," Noir muttered, rubbing his chest. "You're stronger than i imagined. I'll follow you."

Arion simply nodded, satisfaction settling in his chest. This was just the beginning.

"I'm glad to hear it, Noir. Now, I need you to do something for me." Arion's voice was sharp and commanding.

Noir looked up.

"Go. Recruit more demons, especially from your own lineage. I want those with an affinity for darkness, those with power. They will form the core of my shadow army."

Noir's smile returned, his eyes gleaming with the promise of destruction.

Consider it done. You'll have them. The Underworld will tremble beneath your banner."

And with that, Arion had succeeded. Not only had he proven his superiority, but he had also gained an ally—one who would help him reshape the world in his image.