The ancient Heavenly Prison, today's Demon Realm. It could be said to be the great world closest to The Present World.
As a new world born when the ancient Demon Emperor broke open the Chaos World, after long ages of evolution, it still had not completely cast off the threat of chaos.
Even though countless Heavenly Demon Dharma Altars had illuminated this place, their radiance enduring through several great eras, there were always many dangerous regions—like scars the Demon Realm could never heal—preventing this world from being fully connected. It could not possess, like The Present World, fertile civilized lands stretching tens or hundreds of thousands of miles.
In the Demon Realm, there was more than one natural boundary like Frost Wind Valley. From another perspective, they had also left many buffer zones in the war between the Human Race and the Demon Race, a war that had stretched across several great eras.
Where no natural boundary existed, the Human Race and Demon Race each built great cities to face one another, taking the blades of their armies as their border, their slaughter without end.
And among those natural boundaries, Frost Wind Valley was a rather special kind.
In the region surrounding Frost Wind Valley, the boundary between heaven and earth completely separated the two sides, permitting no passage from north to south. Frost Wind Valley was the sole natural route.
Yet frigid winds lingered here all year round. Human or demon, anyone even slightly weaker would freeze at the sight of them and die at their touch. Even the powerful could not endure them for long.
Only during the winter month of every year in The Present World did they briefly disperse.
And that was when the Human Race and Demon Race unleashed their slaughter in Frost Wind Valley.