[quote=@That AWFUL Guy]
Alright, just spitballing here, but how about:

~ Lucis has 13 moons, each corresponding to a zodiac sign.
~ There are different kinds of afterlives for different species/cultures, each with their own designated guide (Valkyrie, Dullahan, Shinigami etc.)
~ Attempts to map the Black Gale have all failed
~ Earth's moon hosts only abandoned colonies
~ There is at least one Ancient Egypt-esque lost civilization in Lucis
[/quote]

If we're doing moons by zodiac sign, I refuse to count Ophiuchus as a 13th sign. So I like 12 moons personally. But good ideas. 

Also, we actually have some established ideas on how we're doing spirituality/lore/mythology in regards to your second point. Other than this, cultures and such will evolve with beliefs they find most fitting regardless, so none of it actually has to be legit to be legit if that makes sense.