I cannot lie, I love religion in gaming. Now, I should be clear about that. Unfortunately many depictions of religion in gaming (or other fiction) is a tedious variant of the 12th century Catholic Church with corrupt priests, inquisitions, and exploitation. That's a tired trope and one that adds a very specific flavour to games. It's the ketchup of religious depictions. If you like your story flavour to be common and uninteresting then do that.
What I'd rather have in a game is a religion that has an appeal to common people, that gives ordinary people a web of meaning to their lives, and that allows for corrupt clerics sometimes. I want a religion that helps explain cultural features or turns of phrase. It has to explain festivals, rites, supersititions, and more! When I started to sketch a religion for my Burning Wheel game I had all of this in mind. I could do no less. So here's my take on a creation myth for O Mortal.
There was Chaos, churning and rolling,
And there was no form.
Then the Four reached into Chaos with their hands
And took some
And shaped it
Forming land, and sea, and sky
And all the lights.
They breathed into it and time began.
Erolti made balance in the days and seasons.
Palsu made the multitudes, in living things.
Urgomath made structure, in the land.
Therokim made turmoil, in the storm and the volcano.
The Four looked and saw the works of their hands.
Erolti reached once more into Chaos.
She brought forth spirits
Playful, perceptive, and balanced.
She placed them into the animals.
She placed them into the streams.
She placed them in all things of the world.
So it is that spirits are in everything.
Then Erolti reached into Chaos again.
She brought forth Elves
And gave them the centuries
And gave them songs
And gave them to the spirits as brethren.
Palsu reached once more into Chaos.
She brought forth gods
Powerful, placed, and plentiful.
She led them to mountains.
She led them to valleys.
She led them to oceans.
So it is that gods rule places.
Then Palsu reached into Chaos again.
She brought forth Humans
And gave them the many features
And gave them magic
And gave them to the world as a many textured rainbow.
Urgomath reached once more into Chaos.
He brought forth gods
Creative, purposeful, and changing.
He showed them the clay.
He showed them the forge.
He showed them the tools.
So it is that arts are homage to the gods.
Then Urgomath reached into Chaos again.
He brought forth Dwarves
And gave them ideas
And gave them gold
And gave them to the mountains to bring forth wonders.
Therokim reached once more into Chaos.
He bought forth demons
Mischievous, hungry, and destructive.
He showed them Chaos.
He showed them the efforts of living beings.
He showed them Chaos.
So it is that demons return all to Chaos.
Then Therokim reached into Chaos again.
He brought forth Orcs
And gave them passion
And gave them caprice
And gave them to the world to punish hubris.
This seemed more fun that just saying, "The Human god is Palsu. Other lesser gods exist and rule over areas." It's also (I hope) evocative enough to give my players a sense of a cosmology, a metaphysics, some superstitions, and some divine explanations for things. Also, since the Gods and gods are real, I get to use all of this in the game. Joy!