There is a slightly awkward disconnect between the moments where the characters speak in a very high formal manner, and some of the internal thinking. 'Play nice' does not fit with any of the wording before, for example. I could not work out who was pleased about the moth spearing. There are some places where the world-building is masterly, such as the Jade seals, and others where it doesn't succeed, such as the master imitation with the finger.
There are a couple of odd word choices - the sentence about the sister creeping under the palace sheets did not work for me, for example. And who was she going to do that with, and whose sister were we even talking about?
All of that said, the picture was painted beautifully. The prologue (it's true, they are less common than they once were) works well. The piece that was missing for me, and this may be about to turn up in Chapter 2 very successfully, was that after a long prologue, the next section is about the same side of the conflict, rather than something from the Dongshan side.
The chapter didn't hook, not yet, but it gives a great introduction to the world. I would turn the page expecting a clearer hook. This could be fixed by a matching scene from the Dongshan perspective. It may be that Kailin is the major character in the book, but I am guessing that there is a protagonist or two on the Dongshan side, and I might move to a section from their point of view, without giving too much away, which illustrates their own stakes/fears/hopes, rather than let this chapter tail off as it does.
It is an excellent start, anyway.