Yes, Teossoxyn is rather obviously the Spirit Talkers. Actually, it's rather disturbing how consistently the spirits of the Xohyssiri seem to derive from their enemies. Tuultox is very probably the swamp people we've yet to meet, and Choxosyn is rather obviously the nomads. Even the Thunderbird, while sort-of representing themselves, also ironically resembles the gods of their other Lowlander enemies.*cough* Look at what's to the north of their territory *cough*
It's not implausible for a culture that revolves around slave-taking to the degree theirs does to heavily integrate foreign gods, but it's so on the nose with them that it really makes me wonder about their culture.