豹頭山 A Fiend at Leopard Head Mountain
其夜有一妖精，離城只有七十里遠近，山喚豹頭山，洞喚虎口洞，夜坐之間，忽見霞光瑞氣，即駕雲而看，見光彩起處是王府之內。其夜有一妖精，离城只有七十里远近，山唤豹头山，洞唤虎口洞，夜坐之间，忽见霞光瑞气，即驾云而看，见光彩起处是王府之内。
逐句解 Line by line
That night there was a fiend some seventy lǐ from the city — the mountain was called Leopard Head Mountain and the cave Tiger Mouth Cave. Sitting there in the night he suddenly saw the rosy light and the lucky vapour, rode a cloud over to look, and saw that the brightness rose from inside the palace.
The monster of the arc arrives in one sentence, eighty-eight lines from the end of the chapter, and the novel introduces him the way it always does: by his address. 豹頭山 and 虎口洞, Leopard Head Mountain and Tiger Mouth Cave, are both named for predators' heads, which is a fair warning. Seventy lǐ is about forty kilometres at the Ming measure — near enough to see a light and reach it in a night.
A chapter with no monster in it at all produces one on its second-to-last page, sitting on a mountain forty kilometres away and looking out of his cave at a light.
The two place names are worth reading together. A leopard's head and a tiger's mouth: the novel names the geography after the parts of an animal that do the damage.
There is nothing supernatural about how he finds them. He sees a glow on the horizon and goes to look, which is what anybody would do.