Right! How could she have forgotten!
In the novel, the female protagonist had come here and picked up a bargain in the form of a formidable treasure. After a little tinkering, that treasure became a powerful defensive implement, and when combined with talismans, it could even be used as a flying apparatus.
In the end, the female protagonist gave it to Qin Xiu, moving him beyond words and making him even more utterly devoted to her.
Chapter 18