I'm pretty sure I've heard Greg talk about this at a con, but can't remember the details. Why do Yelmalio and Humakt have Geases and Gifts but other cults don't, or just have general taboos and required behaviour without the formalism of Geases and gifts.
I think it has to do with them both being Truth Rune cults, but in which case why doesn't Lhankor Mhy have them?
Simon Hibbs