Centerra currently has a monotheism (Church of Hesaya) and it sucks so I'm rewriting all of it, except for the bit where the Church cannibalizes other religions and incorporates them into itself.
Also, I'm going to try to distance it further from Catholicism by calling it the Temple instead of the Church.
This is the thing that is omnipotent. You can't pray to it. It is distant. It created everything.
This is the god of air, and the prime deity on Centerra. He is the Demiurge, and he organized everything.
He lives in a mansion on a mountain top. You can see it from a nearby peak. Whenever you look at it, you can hear the bell of St. Dorbaine ringing in your ears. It stops as soon as you leave. You can approach the mountain, but unworthy souls are struck with weakness as they approach. The blessed become stronger as they approach the Holy Mountain.
Very noble people sometimes trek to the shrine in the valley below the peak.
You can see the mansion, and you can see the guests on the balconies. They are strange and beautiful and some are colossal. If you attract their attention, they'll send you an invitation. (Basically, name-level PCs are expected to go and dine with idle, squabbling godlings, titans, and interdimensional weirdos.)
Zulin is not at home. Zulin is at a tea party in Hell with Ashta Lon Who-Is-Falsehood. Zulin is trapped at the tea party by the conditions of politeness. If Zulin leaves the tea party, Ashta Lon is also free to leave. They've been having tea for a very long time.
Only Priests of the Upper Air are allowed to pray to Zulin, and to receive his miracles. Priests of the Lower Air must pray to a saint, a prophet, or a slave-god.
She is the First Prophet, and as such, is an equal to Zulin. She is the intermediary between the Authority and. . . everything else, really.
Not only did Essa first re-teach the world the teachings of Hesaya after the Time of Fire and Madness erased all history, but she also decided to reincarnate.
She's currently on her 57th reincarnation. Her current form is 10 years old, and enjoys spicy noodles, horseback riding, and small dogs. She is the leader of the entire religion. She is protected by a Brynthic Hound called St. Smaudius. ("Smaudy")
Tar Lath Lien
It is widely believed that the dragon-sorcerer Tar Lath Lien is the "serpent of the apocalypse" described in scripture, who will one day destroy the world. Actually, it's quite clear that he is.
Tar Lath Lien is horribly smug about all this, as you'd expect.
The Eastern Patriarch
This is Yasu's second-in-command, who is in charge of the Temple within the eastern third of Centerra. His position is required for reasons that are political, ideological, and probably more than a little sexist.
There is a growing schism between the eastern and western Temple.
Spirits of the Upper Air
It is accepted that there is a whole secret ecosystem in the upper atmosphere. It is a realm of lightness and invisibility. Invisible wars are fought there, and titanic angel-fauna devour each other with magics that could rend mountains. The greatest of these sky-leviathans weighs less than a feather.
This is where angels come from. Not the false "angels" of the Dawnbringers, but creatures who are strange and translucent (which is holy, because that which is translucent cannot hide anything). Secrets and lies are the tools of Ashta Lon.
Saints become translucent, like purest ice. All you can see are their bones, but even those fade in time. The weather mirrors their moods, obeys their commands. They speak to the wind and learn it's secrets. They also become lighter. They walk on water. Then, levitate. Then, they fly.
Paladins of Hesaya wear no armor except a pale blue tunic, each thread of which is banded with scripture (in tiny alternating blue and white bands, a fantasy analogue to Morse code). They wield long, narrow swords, and when they cut, the wind cuts for them. (50' melee range with their swords.)
Clerics of Hesaya command air. They cannot control the weather, but they control small amounts of air nearby. They can order the air to avoid your lungs, and you will suffocate in X rounds, where X = half of your Constitution (unless you run more than 200' distant).
No longer seem as out of place.
Despite all the magic colleges on Centerra, the biggest singular magical institution is the Temple.
The Temple teaches that the naga taught humanity magic, and indeed, many temples have a resident naga as a teacher and guardian.
Symbols of the Temple
Air and Serpents. (Serpents because they are agents of the Authority, who is represented as an infinite Ouroboros most of the time. Also, the naga thing. Also, giant space snakes supposedly ended the Time and Madness but I've never typed it on the blog before this because it sounded stupid.)
Invisible Stalkers. You never know when they're hanging around.
Coatls. The most famous symbol of the Temple. It's on their coffee mugs.
Air Elementals. The tiny, pissed-off tornado kind. But honestly, if you're fighting an air elemental, everything in the area is going to be whipping around like a hurricane, and you'll have to shout to speak to anyone more than a few feet away.
The Doctrine of the Four Elements . . .
. . . is a heresy. There are many atomic elements, and air is a gas, merely one of the three states of matter. (Fire is really more of a chemical reaction.) It's just that air happens to be the most enlightened state of matter.