Duoer City occupied a delicate geographical position.
The city had originally belonged to the Frank Kingdom, lying in its northern region near the border with the Malo Empire.
A mountain range formed the boundary between the Frank Kingdom and the northern Malo Empire, and Duoer City stood at the mouth of one of the few passable valleys through it, effectively controlling the chokepoint of this major route connecting the two countries.
Previously, the Frank Kingdom and the Malo Empire had maintained good relations and could be considered allies, so Duoer City had served merely as a transportation hub.
Now, with the Frank Kingdom destroyed and the surrounding territory assigned to the Drake Duchy, Duoer City had suddenly taken on immense strategic significance.
If the Malo Empire wanted to invade again, Duoer City was a point it could not ignore.
Thus, when Xu Yi partnered with the Drake Duchy to build a complete urban defense system capable of repelling a Malo Empire invasion, Duoer City became their first choice.
As Xu Yi had said, the initial purpose of developing this system was to provide the entire city with a complete Mana Protection System based on military magic machinery, allowing it to withstand attacks from the Malo Empire's armies with ease.
The ultimate goal was to maintain those defenses even if the enemy deployed Archmages, making Duoer City impregnable.
But this system had one serious problem: its cost was far too high.
According to the Xinfei Merchant Guild's budget estimates, fully equipping even a relatively small city like Duoer City with such a system would require an investment of more than eight million gold coins at a minimum.
So even with the Xinfei Merchant Guild taking charge, there was no way to equip every city currently under the Drake Duchy's control at