Before this, Belti had also said that Night Spirits were an extremely rare kind of monster born only from filth.
They usually appeared only in places steeped in corruption, such as Ancient Battlefields where large-scale bloodshed had once occurred, slaughterhouses, towns ravaged by major plague outbreaks, and other places that had suffered catastrophic events and mass casualties. Only such places could possibly give birth to a Night Spirit.
There was no shortage of such places in the Source World. In fact, there were many.
Yet the only place that met the conditions for the birth of a large number of Night Spirits was the former territory of "that empire"—the Black Land, now cut off from the Source World by the Narnirga front line.
That was where the largest and strongest empire the Source World had ever known had perished. It was the graveyard of countless lives.
The battles fought there and the deaths suffered there were simply beyond counting.
On top of that, it had become the Abyss's largest stronghold in the Source World. There was no place in this world more deserving of being called "filthy."
And several thousand years had passed since the fall of "that empire."
If counted from when the last Savior left the Source World, then it had been eleven thousand years.
For over ten thousand years, "that empire" had also stood at the forefront of the war against the Abyss. Over such an immense span of time, it was only natural that vast amounts of filth would settle in the Black Land and give birth to countless Night Spirits.
Thus, these mass-produced Night Spirits became a weapon used by the Abyss.
Through Reinani's halting, hesitant account, Riezel and Belti finally understood why the so-called Night Spirit Aggregate had appeared here.
They had actually been