Can you elaborate a bit more on what you mean by some of those? Sleep patterns makes perfect sense, and history also works, but I'm imagining that disposition and intelligence doesn't mean that all the good, stupid species go to the Daywalkers and the evil, smart people go to the NIghtwalkers. So how would intelligence and disposition play into the decision? Also, what would they be worshiping?

I won't deny, I'm still slightly concerned about how... abstract it seems. But maybe I'm missing something again.