(Adapted from a comment made elsewhere.)

Religion is not at the foreground of the stories I tend to tell, but it is in the background, part of the “vibe,” so to speak. I tend to stick to versions of a specific cosmogony (Creator+quasi angels+quasi devils), partly because it reflects my own Catholic beliefs, but also frankly because my world-building energy is limited, and most of the time, I’d rather spend it elsewhere.

I started out doing this kind of Generic Monotheism in the vaguely India-adjacent Jaiya books, and continued in the prequel series, Ancestors of Jaiya, on the theory that I was going to get into less trouble riffing on my own religion (a minority religion in India, although it’s been there longer than some things) than I would riffing on other people’s religions. So, there’s some trappings that nod to the practices of the subcontinent, like the tendency of priests to wear saffron, or the depiction of the Immortals as blue skinned(1), but the dominant religion (which is apparently very old and includes many branches) doesn’t map very closely to Hinduism, Islam, etc. You can read the only part of the Jaiyan scriptures that I ever wrote here, and that was partly because I knew from very early on that I wanted to do a Raiders of the Lost Ark type story in that setting. (That idea eventually became Seeking the Quantum Tree).

Star Master, the space opera duology was a bit similar: the humans are descended from the residents of an ancient Egyptian city, who were abducted by space demons and rescued by space angels, who demoted the Egyptian priests to bankers and taught the people about the Kindler, the Supreme Being. The humans’ concern for the respectful treatment of the dead is probably their most obvious link to their old belief system. As in the Jaiya books, there are passing references to the idea that the priests don’t agree on everything, but it’s just not relevant to the plot. As in the Jaiya books, there’s an implication that the space angels are no longer very hands-on with the humans. One of the space angels claims that they are themselves too “binary” to be all that helpful to humans: This is why we find it hard to guide your kind, why we mostly keep our distance. We and the [demons] are binary: yes or no, good or evil. There is no room in us for the thousand shades of ‘maybe’ each human contains.

The Hunter Healer King books have a steampunkish, Central European vibe, backed by a vaguely Tolkienian mythos (although he would not have approved of either the steampunk bits or the Charlemagne bits). It’s a little bit Ruritania, a little bit Jules Verne, and a lot Hammer Films, so the “vibe” requires blessed objects, temples, dioceses, priests, high priests and Priest-Electors (to match the Bishop-Electors of the Habsburg Empire).

I haven’t really gotten very far into the details in the actual trilogy, but here’s a little inside-baseball on this setting: There were something like the Valar, once upon a time: the Immortals, spirits who incarnated in humanoid bodies. Some of them went bad, some of them stayed good, but once their physical forms were slain, they were banished from the visible world…and in the present day of the trilogy, that means all of them. Almost all of these beings, good and bad, intermarried with humans, producing long-lived “Demi-mortals” similar to Elves. The Demimortals were never numerous, and they in turn intermarried with humans, to the point where they stopped being a separate population. Their bloodlines live on in a couple of populations of long-lived, unusually durable humans, of which the Stormcrows (think Gothic Steampunk Dunedain, descended from the Faithful of Steampunk Numenor) are the most prominent group.

(1) Although I think I initially imagined the Immortals, the good Vazata and the evil Avazata, as looking like the aliens from Avatar, which in turn were probably influenced by depictions of Hindu deities. So the influence there would be an indirect one.