It seems like a lot of hypothesis, but there's a decent amount of evidence. One thing that I noticed in this show was that Ah Mah absolutely loathed Kai Yee, on a level that she didn't even display to HAM. It puzzled me greatly, because even if he was an evil Te Xuan Ze, the vehement hatred she had for him seems uncharacteristic. But if this is the case, if Kai Yee is responsible for the Veil, the Barrier, all of that, then any Te Xuan Ze would hate him for what he did to them. You will also notice that Jasimine called Kai Yee "Their Greatest Curse". Further evidence for my theory.
What else can we gather from this episode? Well, we know that Monroe trained Kai Yee, as he was the aide to the Te Xuan Ze during the banishment of Auntie Roon. It is as such interesting that Monroe was not there to help Jasimine fight him, but it's possible that seeing his greatest failure again would be too much for the Scottish advisor. It is an interesting prospect to think about. Monroe's failure to teach Kai Yee the restraint necessary could have been because the imminent war between Magic and Humanity. Something tells me that Monroe's never really shrugged that off.
Anyways, that's my theory. If you have any thoughts or criticisms, feel free to post or IM me.