I'm very interested in the origins of the Nonmen and how they relate to regular humans. I'm interested in the origins of Earwa in general, really. The lack of any creation myths in Inrithism and even the other big religions (Fanimry, Zeumi, Scylvendi) is ridiculously suspicious considering the nature of religion in the series.
In that vein, I'm most interested in learning more about the higher metaphysics of the Bakkerverse, namely the Hundred, Damnation, and stuff like the Psukhe, Inverse Fire, Judging Eye, etc.