It was an old-fashioned introduction; Hao Ren could not help but think of it that way.
The ancient civilization plunged into the gap of space and time following an unknown disaster (the explosion of the divine realm). The world on the surface was destroyed, and the survivors barely survived in the shelter that they built inside the planet with their powerful technology. As time went by, the disaster on the planet's surface subsided. But the survivors in the underground shelter had mutated or simply died from the perennial isolation as well as environmental changes. The shelter that they left behind became the dangerous Great Pit—a place that was filled with deadly poisonous gas and monsters. The civilization on the surface avoided it like the plague.
