Somewhere in the depths of the Great Forest of Darkness
On the higher slope of the tallest mountain within the vast and dangerous forest, a huge, unnatural cave that seemed to have been made by something can be seen.
The cave was rounded and spacious, measuring around two hundred meters in diameter. An area so vast and wide that hundreds of people could fit in it.
The interior was not what one would expect in a cave, being so rough and rocky. Instead, the walls, ceiling, and floor were surprisingly level and had smooth surfaces.
The stones were polished to the point where they could reflect light. The entrance was the only opening of the cavity and the only way to get inside and out of the cave.
It was strangely unusual for a cave to have those features, unless the cave was made by humans. But no humans had ever reached the mountains, let alone climbed their summits.