Religion is much more nebulous in Sai'is than in most D&D settings, functioning as it does in the real world, with a great deal of faith and doubt, respectively. There are stories of miracles and the like, but no tangible proof. Related to this, there is no resurrection magic in Sai'is, although undead do exist.
Clerics as a class do not exist. Priests wield no special power.
Paladins do exist, but it is unclear where their magic comes from.