I took a major step in developing the The Arch of Time fantasy universe in 1987. A new role playing game was released. I decided to create a supplement to the game--religious role playing.
The supplement had two parts. One part was counsel on using religion in role playing. Since role playing games are viewed negatively by some religious denominations, I advised players not to use gods that had ever been worshipped in earth's history. Game masters should create their own gods or use gods made from whole cloth, such as I provided in part two of the supplement.
My view was that if one used a god such as Cernunnos, the irate denominations would "demonize" the game, no matter that the players, in actuality, viewed the god as a prop and not as a deity that they revered. The denominations would draw parallels between that stag-horned god and another horned figure from their own religion.
Perhaps nothing could inoculate the role player from the charges of those who demonized anything beyond their scriptures. But in my view, it was prudent to do what one could to appeal to the reasonable end of the spectrum.
I further counseled players that the important aspect of using religion in role playing was that religion could enrich the game environment and the players' conceptions of the roles that they played. The precise amount of damage that Odin's spear does is irrelevant to the role play. So my emphasis was on building a fictional world, not on game mechanics.
The supplement also had to create specific abilities and rules for players of priest roles. In role playing games, the in-game physical struggle is somewhat important. The players want to defeat the enemy. Many games are set up so that the players battle a great many enemies in a playing session with no time to fully rest and recouperate in-between combats.
Games (including the game that I wrote the supplement for) traditionally used the priest class to heal wounds. Who/what the priest's god is like should affect the abilities of the priest, not just his outlook on the world.
As I looked over the set of myths that defined the gods in my supplement, I realized that few priests in my universe fulfilled their usual roles. Some priests would be warriors, skilled beyond human abilities. Some would be scholars who had some mental/esp/communications abilities. Some would have many abilities similar to elemental wizards, harnessing fire, for instance. But some priests would mostly heal.
This made my universe into a something that I had never seen in fiction--a fantasy world where some characters have abilities that work similarly to magic, but are religiously based. If I put magic in the hands of the gods, how would my literary universe work?
Do I know that this concept is unique? Of course not. How can one ever know that he has a unique literary creation, since no one has read everything. For instance, a couple of days after I patted myself on my back for creating an excellent name for a street in my city of Tistrin, I found that George R. R. Martin had the same street name in one of his novels. And GRRM may not have been the first to "invent" that name.
In any case, I enjoy exploring a world with wizard/warrior/scholar/mentalist/bezerker/ninja/healer priests.
If you want to explore, you can find excerpts of stories on my website. You can also find my cosmology there--the story of the gods.