Okay - here's a first pass at gods and the like...
In the Midlands, the primary church is the Church of the Path (or the Church of the True Path). The God of the Path is the Creator of all that is and the revealer of the way to paradise (thus the God is also associated with Light and with Truth and with Life). From the Western Alliance (I need a new name, since I think this was used in Mystara or somewhere...sigh) to the Frontier, most people worship this God, and simply call him God.
As the Church of the Path is a relic of the Old World, there is no center of power, no uniformity of doctrine or practice. Thus, while all the faithful base their beliefs on the same holy books, their expression of that belief is varied. The oldest worship center is actually in the South - at the Fortress of the Knights of the Crescent Moon - from before the Great Storm.
Other gods are worshipped - notably, the Old Gods - elemental forces (often of evil) as well as demons and devils. Many ultra-powerful creatures are worshipped and are able to confer their power onto their servants (see below). Lesser local gods are also worshipped.
Druids are also present in the Midlands, keepers of nature and balance, they at times draw power from the old gods, sometimes from nature. Druids all have Neutral as a component of their alignment, though they may be good or evil, lawful or chaotic - often opposing one another.
Powerful beings can bestow their power on their servants. When the being who is worshipped is dwelling on his/her plane (the Abyss, the Elemental Planes, etc), he/she is able to grant spells & abilities in a fairly unlimited fashion, though each prayer or miracle actually draws on the essence of the worshipped being. Since the cost to the being/creature is actually very small, generally they are granted without any notice. If a servant displeases the being/god whatever, the power can be intentionally withheld, essentially stripping the servant of any powers.
However, if the powerful being is present in the Prime Material Plane, he/she is limited in power - even if only an avatar of the being is present and not the being itself. Then, the god/demigod/power or whatever grants its powers at the cost of hit points (one hit point per spell level granted). Such hit points are regained at a rate of 1d20 per round. If a worshipped being is reduced to 0 or fewer hit points while on the Prime Plane, the being is rendered powerless for a round and can be effectively trapped in a statis or sleep if the proper (dangerous) incantations are known and the proper (even more dangerous) rituals are followed.
Trapped gods/beings can still be tapped for power, but with the restrictions indicated above (they are trapped on the prime plane so they are limited in how much power can be drawn from them, though generally they are unable to withhold that power, since their consciousness is, in essence, numbed). Thus, the incredible irony of the more followers of the trapped gods try to use arcane means to free their god, the less power the gods have. Releasing a god/being from this stasis is equally complicated and dangerous.
Thus, the Old Gods are all trapped in this Stasis, though their followers can still draw on their power. Likewise, a number of powerful demons and devils are trapped, though they, too, have worshippers.
Clerics, then, draw on the essence of the being/god they worship for their abilities, prayers, miracles. However, they also expend their own spirit (fae) in much the same way magic users do. As clerics get more powerful (higher levels), they can actually become more powerful than the beings they worship. Thus, the gods/beings/etc often feel threatened by their most powerful followers and may choose to withhold their power from them or challenge them. The followers, however, may be of sufficient power to defeat the being/creature and may choose to take its place (and thus the worshipped becomes a worshipper) or to become a power of his or her own (demigod, if you will).
RIP Stephen Lee Lortz 1949-2017 - I just learned via Jennell Jaquays that Stephen Lortz (September 7, 1949 - April 23, 2017) passed away yesterday. Stephen Lortz was another of Dave Arnes...
1 hour ago