Wasteland Ruins

I accidentally ran into a group of tomb robbers while collecting poetry... What is the ancient country mentioned by the tomb robbers? What does the mysterious disappearance of the foreign soldiers a hundred years ago have to do with the destruction of the ancient country? Is there some connection between the mysterious girl and the destroyed ancient country? What is the connection between the zombies in the ruins and the gods believed in in the ancient country? On the missing great-great-grandfather's sword and the stone statue of a mythical beast worshiped by the ancient Chinese?