The Greatest Assassin Gets Reincarnated in Tensura

Arion, ever the meticulous strategist, had spent years gathering intelligence from the shadows. His network of spies stretched across every nation, from the grand empires of the east to the isolated kingdoms of the north. He had walked among the commoners, listened to the grievances of rulers, and observed the chaotic struggles against monster attacks.

It was clear—there was no unified system to deal with the rampant monster infestations. Each nation had its own military or mercenary groups, but they lacked coordination. Worse yet, corruption and bureaucracy often hindered responses, leading to unnecessary loss of life.

Then came the idea.

A guild. An independent organization, free from government control. A place where warriors, mages, and skilled individuals could register, take on requests, and earn their way through monster hunting, exploration, and other tasks.

But establishing something so grand wasn't just about building a guild—it was about making it indispensable. That was where Arion's spies came in.

Arion immediately dispatched his most trusted spies to begin the groundwork. These spies were no mere informants—they were infiltrators, manipulators, and master tacticians who had spent years weaving their way into the power structures of various nations.

Their first move was spreading the need for a guild.

They infiltrated noble courts and whispered about the inefficiency of current monster-hunting efforts.

They bribed local merchants to spread rumors of a rising monster population and how independent hunters were dying due to lack of organization.

They even orchestrated staged monster attacks in key trade routes—nothing devastating, just enough to shake the confidence of leaders.

This gradual destabilization made rulers realize that relying on their own forces was unsustainable. They needed outside help.

Once the fear and demand were established, the spies moved to the solution phase.

In select nations, Arion's spies disguised themselves as influential merchants, scholars, and former knights, proposing the concept of an independent monster-hunting guild. They approached rulers with carefully curated data—exaggerated reports of rising monster threats, charts showing how much their current defense forces were costing them, and a comparison of how a guild system would be more cost-efficient.

The pitch was simple:

The Guild would take responsibility for handling monster subjugation requests.

Governments would not have to allocate their own forces.

Adventurers would fund themselves through monster hunts.

Guild-affiliated nations would gain access to a free-flowing workforce of strong individuals without committing their own resources.

To further sell the idea, spies went as far as hiring rogue mercenaries to pose as "freelance adventurers" who conveniently saved villages from staged monster attacks—only to lament the lack of an official guild to regulate and protect adventurers.

This strategic fear-mongering worked flawlessly.

One by one, nations saw the value of an International Adventurers' Guild, not realizing they were falling into Arion's carefully laid trap.

With nations convinced, Arion sent another division of spies—this time, engineers, architects, and enchanters—under the guise of a powerful merchant guild looking to invest in infrastructure.

The central guild headquarters was built in the western region, strategically placed,

ensuring its independence. The HQ was a towering fortress-like structure, reinforced with magic, filled with training grounds, massive libraries of monster knowledge, and state-of-the-art equipment for adventurers.

Simultaneously, branch guilds were discreetly established in every affiliate country. These smaller guilds acted as recruitment and request centers, ensuring that no nation felt left out.

With the infrastructure ready, the next step was spreading influence and control.

Once the main guild was operational, Arion used his spies to manipulate public perception in two ways:

Using Bards and Storytellers

Spies disguised as traveling bards went from city to city, singing exaggerated tales of legendary adventurers slaying massive monsters under the guild's banner.

Locals started talking about how guild adventurers were protecting towns better than national armies.

Artificially Creating High-Ranked Adventurers

A few elite spies were publicly planted as S-rank adventurers, performing grandiose acts of heroism to draw in recruits.

These adventurers would defeat major monsters in public with ease, making common folk idolize them and flocking to join the guild.

Soon, every young warrior, rogue, and mage wanted to be an adventurer.

This rapid popularity forced even hesitant rulers to officially recognize the guild—or risk falling behind.

With its dominance solidified, Arion implemented a strict ranking system:

S-Rank – The elite, capable of slaying the most powerful creatures and leading expeditions.

A-Rank – High-tier adventurers, veterans in battle and specialists in various fields.

B-Rank – Seasoned adventurers, capable of handling large-scale threats.

C-Rank – Intermediate adventurers, reliable but still growing.

D-Rank – Beginner adventurers, handling simple requests.

E-Rank – Newcomers, barely battle-tested.

Every adventurer was given a Guild Card, a magically enhanced identification that:

Tracked their rank and completed quests.

Allowed them free travel between affiliated nations.

Gave them access to guild-exclusive resources (training grounds, libraries, and magical workshops).

Quests were categorized:

Monster Subjugation – Hunting dangerous beasts.

Exploration – Mapping unknown territories.

Escort Missions – Protecting merchants, nobles, or artifacts.

Resource Gathering – Collecting rare herbs, ores, and monster parts.

With the guild now a powerhouse, Arion ensured long-term dominance by placing his spies at the very core:

The Guildmaster was one of his most loyal operatives.

The ranking examiners were all pre-selected by him.

Every branch guild had a spy overseeing operations.

Even guild receptionists had secret directives to keep adventurers from questioning the guild's power.

On the surface, the guild was a neutral organization that benefited everyone.

In reality?

It was a global intelligence network, with every powerful warrior unknowingly reporting to Arion.

Now, with nations dependent on the guild and adventurers thriving under its banner, Arion had silently seized control of the world's strongest military force—without ever drawing his sword.

The Adventurers' Guild was not just a system for hunting monsters.

It was the perfect cover for global domination.