The Greatest Assassin Gets Reincarnated in Tensura

As Arion and Veldora stepped out of the special dimension, time in the real world had barely moved. Only one day had passed, but for them, it had been ten long years of battle and growth.

Now, it was time to establish their stronghold.

Arion closed his eyes and spoke within his mind.

"Pandoria, scan my memories. Find the perfect blueprint for our base. It should be a city—a sanctuary for shadow assassins, a place of ultimate training, relaxation, and refinement. It must be hidden from the world yet capable of emerging when needed. It must be adaptable, ever-changing, yet absolute in its form."

Pandoria's voice resonated within his consciousness.

"Understood. Analyzing… Constructing the perfect design… Done."

The Shadow Citadel would not be a mere fortress—it would be an entire city, woven into the very fabric of the void itself.

Its Core Feature:

The city exists in a pocket dimension linked to Arion's Abyssal Horizon, allowing it to appear and disappear at will.

It can transform and reshape itself, adapting to different needs—whether for war, peace, or expansion.

The entire city is enveloped in a living shadow barrier, rendering it invisible to all who are not permitted entry.

The environment within the citadel is controlled by Arion's will, allowing for day-night cycles, weather changes, and even seasonal shifts.

At the very heart of the Shadow Citadel stands the Void Throne, a massive, obsidian-black tower that stretches into the endless night sky.

This tower serves as Arion's command center, where he and the strongest members of the Shadow Order reside.

The topmost chamber holds Arion's personal quarters, a vast space with a sky dome that reflects the abyss.

It contains a Grand Strategy Chamber, with an ever-changing holographic map of the world, allowing for real-time surveillance of key locations.

The Hall of Shadows, where elite assassins train in advanced shadow warfare and receive missions.

A dimensional archive, containing the knowledge of ancient civilizations, combat techniques, and forgotten history.

The tower's walls are embedded with abyssal energy, making it impossible to breach unless permitted.

The Assassin's District - The City of Silent Blades

This sector of the city is where the shadow assassins reside, train, and sharpen their skills.

Housing: Luxurious yet simple homes made of black stone and ethereal mist, merging seamlessly with the environment. These houses can shift locations based on the will of their owners.

Training Grounds: An expansive underground facility equipped with illusion-based battlefields, gravity chambers, and endless mazes designed to push assassins to their limits.

The Abyssal Tower: A deadly challenge where assassins must navigate through 100 floors of evolving dangers to test their growth.

Weapon Smiths & Enchantment Chambers: Hidden deep within the district, masters of void-forged weaponry craft and enhance gear that can cut through dimensions.

Shadow Market: A bustling underground market where rare artifacts, forbidden knowledge, and specialized tools are exchanged.

The Warrior's Haven - The District of Unyielding Might

This district serves as a sanctuary for warriors, duelists, and battle-hardened fighters.

Coliseum of Eternal Combat: A vast arena where warriors can engage in battles that simulate real war scenarios—from one-on-one duels to massive battle simulations.

The Hall of Titans: A monument to legendary fighters, with enchanted statues that allow warriors to spar against echoes of historical champions.

The Combat Academy: A grand training facility where fighters of all disciplines train in swordsmanship, hand-to-hand combat, magic, and assassination arts.

Battle Meditation Chambers: Where fighters can relive their past battles, refining techniques and strategizing for future confrontations.

The Sanctum of Tranquility - The Leisure District

Despite being a city of warriors and assassins, the Shadow Citadel offers places for rest, rejuvenation, and pleasure.

Japanese-Style Public Baths: Vast, naturally heated onsen with mystical properties that heal wounds and refresh the mind.

The Abyssal Sauna: Infused with void energy, this sauna accelerates muscle recovery and energy restoration.

Celestial Gardens: A breathtaking park with floating islands, glowing trees, and eternal night skies to create a peaceful atmosphere.

Grand Restaurants & Taverns: High-class dining areas serving exquisite dishes from all dimensions, prepared by world-class chefs.

The Lunar Lounge: A mysterious bar serving elixirs, abyssal cocktails, and drinks infused with power.

The Phantom Playground - The City of Shadows' Future

For the next generation of assassins and warriors, the Phantom Playground is a sector dedicated to children, students, and apprentices.

Shadow Academy: A special school where young warriors and assassins train under the guidance of elite masters.

Playgrounds & Simulated Worlds: Safe yet challenging environments where young trainees can play, explore, and develop their skills naturally.

Hall of Future Champions: A record of every promising warrior, displaying their achievements and progress.

The Abyss Gate - The Transport Nexus

A complex teleportation system linking the Shadow Citadel to major locations across the world.

Dimensional Gates: Portals that can be used to teleport directly into enemy territory or escape at a moment's notice.

Void Rail System: A high-speed shadow transport connecting different districts within the citadel.

Stealth Ships: Floating warships capable of phasing between dimensions, used for strategic assaults or reconnaissance missions.

The Shadow Citadel can shift its entire structure, changing layouts and architecture depending on need.

In stealth mode, the city disappears completely, existing only in Arion's pocket dimension.

During war, the entire city can morph into a fortress, with defensive barriers, hidden artillery, and war gates that can summon reinforcements from other realms.

As Arion finished constructing the Shadow Citadel, Veldora stood frozen, his mouth slightly open.

"You… actually built an entire city… in an instant?"

Arion smirked. "It was necessary. We need a place for the strongest to gather."

Veldora burst into booming laughter.

"Hah! This is beyond impressive! I've seen countless civilizations, but this… this is a masterpiece!"

He threw an arm around Arion's shoulder. "Alright! I'm staying here for a while! I gotta experience all this firsthand!"

Arion simply nodded.

The Shadow Citadel was complete.

Now, it was time to begin the next phase of their mission.

As Arion and Veldora wandered through their newly built Eminence of Shadow, the air was thick with the weight of their accomplishments. Every corner of the city was a testament to their vision—a city of shadows, a fortress of assassins, a sanctuary of the strongest.

Veldora was visibly impressed, his golden eyes gleaming as he took in the grand architecture, the mystical energy radiating from the walls, and the sheer scale of the project. Despite his usual carefree demeanor, it was clear that even he could not deny the magnificence of their creation.

As they finally entered the Central Tower, where their residence awaited them, Veldora wasted no time.

"Hah! Finally! I thought we'd never get here!"

With a dramatic leap, he jumped onto one of the luxurious beds, sinking into its plush comfort with a satisfied groan. His massive dragon form may have been imposing in battle, but right now, he was nothing more than a big child enjoying his new home.

Arion, watching the dragon lord with amusement, let out a quiet chuckle. He sat down on a nearby obsidian sofa, exhaling as he gazed out through the glass-like abyssal walls, which reflected the eternal night sky of the citadel.

For a moment, there was only silence, a rare, tranquil stillness that neither of them broke. It was the kind of peace that came before the storm—before the war, before the chaos, before the world came crashing down.

Then, Arion spoke.

"Veldora."

The dragon lord lazily cracked one eye open, his expression half-bored, half-curious. "Hmm?"

Arion's gaze was sharp, focused. "We need to establish our next course of action. Now that the Eminence of Shadow is complete, we must begin preparations for our presence in this world."

Veldora stretched his arms behind his head, smirking. "Tch. You're really all about planning, huh? Can't we just enjoy our victory for a little while?"

Arion chuckled, shaking his head. "Enjoyment can come later. Right now, we need to move before the world even realizes what has happened."

Veldora sat up, crossing his arms. "Alright, alright. So what's the plan?"

Arion leaned forward slightly, his fingers tapping against the armrest. "First, since you're already known to the world, you will need to make an official declaration."

Veldora raised an eyebrow. "A declaration?"

Arion nodded. "You will claim the entirety of the Jura Forest as your territory. No one will be allowed to enter without your permission."

Veldora's expression shifted from curiosity to pure delight. He puffed his chest out, laughing heartily. "Hahaha! Now that's more like it! The great Veldora, ruler of the Jura Forest! It has a nice ring to it!"

Then, after a brief moment of realization, he cleared his throat, his face flushing slightly. "A-Anyway, it makes sense. If I claim the land, no one will dare question it."

Arion smirked. "Exactly. Your reputation is already powerful enough to keep most forces at bay. We will use that to establish an untouchable sanctuary—one where we can build our strength without outside interference."

Veldora grinned, leaning back against the bed. "Hah! Leave it to me! I'll make sure the whole world knows that Jura is under MY protection!"

Arion simply nodded, satisfied with the dragon's enthusiasm.

Arion's expression turned more serious. "Next, while you solidify our hold over Jura, I will begin recruiting soldiers."

Veldora tilted his head. "Soldiers? From where? The monsters in the Jura Forest?"

Arion's golden eyes gleamed. "Not just monsters. I will gather warriors, assassins, and spies from all walks of life—beasts, humans, demons, even forgotten races. I will seek out those with potential and bring them into the fold."

Veldora let out a low whistle. "So you're planning to make an army of shadows, huh?"

Arion nodded. "Yes. An army that the world will never see coming. One that exists everywhere and nowhere at the same time."

Veldora scratched his chin, looking impressed. "Hmph. I have to admit, that sounds pretty damn interesting."

Arion continued. "Beyond mere warriors, we need to establish a vast intelligence network. Spies, informants, deep-cover agents hidden in every major power across the world. If a war is coming, we will always know about it before it even begins."

Veldora's grin widened. "Heh. You're a dangerous man, Arion."

Arion smirked. "We have to be. If we are to control the board, we must place our pieces carefully."

Veldora leaned back again, folding his arms behind his head. "So let me get this straight. First, I declare Jura my territory. Second, you build an army of shadows and spies. And third…?"

Arion's eyes darkened. "Third… we begin manipulating the world from the shadows. We make sure that every kingdom, every empire, every faction unknowingly plays into our hands."

Veldora let out a deep, amused chuckle. "Hah! You're really planning to turn the world upside down, aren't you?"

Arion's voice was calm, yet firm. "We must be prepared for what's coming.

Veldora smirked. "Hah! Alright, alright! I like it! This is getting exciting!"

He pointed his finger at Arion. "But you better not expect me to do all the talking. I'll make my declaration, but YOU handle all the boring spy work!"

Arion chuckled. "Naturally."

Veldora let out a satisfied sigh. "Fine then. Tomorrow, I'll make the announcement. And after that… we'll see just how ready the world is for our game."

Arion nodded, his golden eyes gleaming in the abyssal glow of the room.