Because I expect the unexpected, I think the masked man is actually the mastermind behind the killing of Zang Hai's family. He wanted to find the hidden treasure so he used Zang Hai to obtain it, while also using him to eliminate the two persons he no longer needed who's also threatening his safety/interest.
Or maybe he's actually from another country who wants to shake and ruin the Ming dynasty foundation. There are already 3 important people down. And at least another 3 (+1 if the masked man and the mastermind are two different people) to be brought down. Maybe Dongxia people since FL is a Dongxia princess and owns a lot of entertainment shop that's like information center and later she could be forced to pick side to escalate the game. Is crossdresser Mr Eight also come from another country? There's nothing being mentioned so far, maybe I missed it.
Just a theory.
