The world does have religion, but there is no god to be prayed to to gain clerical spells. Everyone knows and it is not disputed that there is a creator who made the world. Everyone knows that there is a dark one that is sealed away. Everyone knows that the seals will eventually burst and that the dark one will be loosed and that it will be the duty of the Dragon (an eternal spirit that is born into different bodies when the need arises) to stop the dark one and seal him up again and set the cycle of breaking free and sealing up anew.
The one power is literally that, it covers everything that is possible (spell wise, including healing). A Channeler (a Wilder or an initiate) starts with only the ability to be able to cast from a certain talent (School), by spending a feat they can buy another talent (School), the talents are, Balefire, Elementalism, Illusion, Healing, Warding, Traveling, and a few others, 9 total I believe.