Experia - Goddess of Heroes

D&D isn't really made for monotheism - for the most part the game basically assumes some sort of barely-present polytheistic world view where everyone just kind of gets along. (There is potentially a storm coming there, as differing portrayals of religions gets labelled "problematic" the same way as portrayals or race have been. Or maybe not - we'll see. Anyway...)

These days, if I were to craft a monotheistic setting, the way I would do it would be as follows:

• Firstly, divorce all PC capabilities from any named higher power - Clerics get their power directly from their Domains, Paladins from the Oaths, and so forth. So no alignment restrictions, no expected tenets or behaviours, etc.
• I would then introduce a single deity, Experia, a goddess with no alignment, no temples, or tenets, and indeed no worshippers as such.
• However, what Experia is interested in is heroes. Where she empowers certain beings, her Chosen, as heroes, beings who are uniquely capable of learning and growing in an exponential matter by the completion of heroic tasks. In effect, they are the only beings who can gain Experience Points.

I suspect that the world most likely to come from this would turn out to be something like "Masters of the Universe" - a number of brightly drawn heroes, a mostly content populace around that, and several forces keen to tear it all down. Of course, combine that with the notion of having several factions (Humans, Elves, Drow, Orcs, Giants, Undead...) and the setting more or less writes itself.

Though I probably wouldn't include either Orcs or Goblins nowadays - if I included nonhuman species at all (very doubtful), I'd replace those with Goliaths.