According to Heiserana, the "mysterious space" had been discovered after a small collapse occurred in the quarry. As an excellent source of building stone, this mountainous area had been excavated by the Heiserana Family for over half a century. The various experts the family had hired had also long since conducted comprehensive surveys and mapping of the entire area—mainly because Heiserana had always been obsessed with digging up treasures from underground. So, in theory, if there had been any mines or natural caverns underground, they should have been discovered long ago. Yet after the previous small collapse, a cavern that logically should not have existed appeared in a corner of the quarry.
The cavern was extremely deep, and its end led to a vast space. If this thing had really been hidden underground from the beginning, Heiserana would definitely have strangled every geologist she had ever hired—at least, she had thought about doing so in her mind.
The cave had initially been discovered by two human workers. Under their foreman's orders, they had gone to inspect the equipment damage and cracks in the rock strata caused by the collapse. A crack in the rock wall that had clearly appeared because of the accident sparked the curiosity of these two reckless fools. No one could say what had possessed them to crawl inside and take a look instead of hurrying back to report it. Perhaps the several bags of marijuana found in their dormitory explained part of it. In any case, these two explorers, high as kites, crawled into the crack in the rock wall and discovered an open cavern inside.
The exit at the end of the cavern led to an ancient city.
They might have seen other things in the cavern. Or perhaps the ancient city still contained poisonous