This was indeed a clichéd development—Hao Ren couldn't help thinking so.
The ancient civilization of the previous era had been dragged into a rift in space-time by an unidentified disaster—the explosive destruction of the divine kingdom. The Outer World had been utterly destroyed, and the survivors had relied on advanced technology to build enormous shelters inside the planet, eking out a miserable existence within them. As time passed, the disaster on the surface gradually subsided, but the survivors in the underground shelters, isolated from the outside world for years and faced with drastic environmental changes, lost their civilization and became monsters—or simply died out. The shelter facilities they left behind became the dangerous "Great Pit," filled with lethal poisonous gas and monsters that never ceased. The new civilizations of the Outer World regarded them as threats to be avoided at all costs...
Hao Ren could even make a bold guess: if these assumptions were correct, then the so-called poisonous gas in the Great Pit was actually the normal atmospheric composition of this planet ten thousand years ago. It had been the foundation on which the previous civilization depended for survival, but had become a disaster for the ecosystem of the current era.
But could a mere ten thousand years truly produce such enormous changes? Or had some other cataclysm occurred here after the planet was dragged into the Dark Domain, greatly accelerating the process of ecological evolution?
They would probably only be able to understand these questions after entering the Great Pit.
He had originally thought that becoming a mercenary in such a muddled fashion and signing a protection contract with a reckless female mage was merely an insignificant interlude. He had never expected it to lead directly to such crucial information. Hao Ren could only marvel at his luck.