Charles named this fortress Millstone Fortress.
The name itself showed just how highly Charles regarded this fortress.
The fortress walls were exceptionally sturdy, built from cooled volcanic lava combined with Imp Nutrient Packs.
There was no need to even mention the thickness at the base of the walls—they had been built directly against the mountain itself.
With such thickness, there was no need to worry about devils breaking through the walls from below.
Even the walls at the top were a full twelve meters thick, while the base was even thicker.
After the walls had been completed, vast amounts of lava were poured over their foundations, further reinforcing their defenses.
Along the walls, a tower stood every twenty or thirty meters, responsible for aerial attacks. Each also housed large numbers of Ratman archers to attack enemies below.
Every brick and stone in the walls had been infused with runes, whose purpose was to strengthen the walls' defensive power.
With the endless influx of magical power from the lava below, there was no need to worry about these walls exhausting their magic resistance.
At the same time, like the other walls, Charles's walls would continue to be strengthened by fire magic.
For now, they could only withstand spell-like attacks from Intermediate Demons, but in the future, they could be strengthened to resist attacks from Greater Demons.
Charles had embedded third-tier defensive spell arrays into every tower on the outer wall.
When battle grew fierce, activating these arrays would allow the towers to withstand a tremendous amount of firepower.
They could even enhance the power of the demons' thrown spell-like attacks.
In this regard, Charles had drawn inspiration from the methods Four-Ring Wizards used to build wizard towers.
It was just that this technology was still far too crude.
It was utterly