I really enjoyed this chapter, and the conflict it creates for Tavaris. First, his desperation over aveline borders on the pathetic – in a good way. I feel like a lot of people have been in a situation or known someone who's held on to a relationship far to long after it's over, searching for a reason to explain why it failed. I also feel like it's impossible for him to get back with her, the way you've set this up so far, so I see part of his character arc will be letting her go rather than getting her back. I also love the religious/personal conflict of his past life.
He might be as self-pitying as Medora, but I think I like him more as a character because he still manages to be funny.
All that said, I found two parts confusing. As sacred as this rite seems to be, Tavaris snuck out of the line to look at the chimp far too easily. It might be more reasonable to just have him whisper from the line, and then have renn threaten him for breaking decorum.
I didn't mind the flashback, because it doesn't real constitute one. But the setup confused me. I can assume parts were intentionally vague, but I never quite understood what the treaty covered. My biggest problem, though, was trying to figure out if jenna and el were from the same country, or merely of the same faith and in an alliance. I think it was an alliance, and that El's country would be the next to fall – a sort of chamberlain and hitler setup – but i wasn't sure if seria was a religion or a country. You've been subtle with most of your exposition, which is good, but i think in this case you could have been a tiny bit more clear. I was only able to figure this out on my second read-through, when i was deliberately looking for answers.