Well, that was a willies inducing post for sure!
So...ok, I've been struggling with this, but I think it might be interesting if...well, I don't know if you'll like it, but here goes:
I want Yerbol to get captured by the Xiis.
Now let me explain why:
-The Xiis are still few in number and need strong figureheads. Illesia(our female Xiis baddie) identifies the capture of both Aria and Yerbol to draw out the "most powerful" of society (ask me to clarify if need be...hamlet has my brain all >_<)
-With the Xiis basically concentrated in that one location, the odds are stacked against all of them making it out alive. Yerbol, being Yerbol, would want to sacrifice himself for the group to make it out alive.
-There's also the draw of Illesia to Yerbol because...well, if you haven't guessed it, she's rather in touch with her physicality. She would see him as a way to begin reproducing even more powerful Xiis(seeing as they're already hybrids) and...well, she would see him as an object to be used(man, this is super dark xD)
-Yerbol would also be able to tip off Aria where he was at and bring her wrath upon the Xiis xD
Think this would fit? Let me know if I'm crazy and then I'll post accordingly