Story in development for videogame

im currently coming up with a story that will either be a videogame, book or comic. 

inspiration: religion mainly christianity and catholicism, the story of the two angels claimed to be reincarnated into human beings, the divine comedy of dante aligheri, and the enochain language 

the story will taken place during the french revolution, and then a trip to the nine layers of hell, seven layers of purgatorio and the nine layers of heaven

the main character may appear as a child, they be secured in a cathedral. they basically have like unholy powers lucifer gave them and the clergy keeps watched of them: possibly will be an antagonist 

i have four characters completed three are demons and one is angel :>

the characters are Alichino, Malacoda and Libicoco original characters from the divine comedy and my own original character in the angel hierarchy they are a power

two other human characters will be exorcists(?): possibly will be changed to main characters

many cool famous philosophers will be mentioned/referenced 

space

conflict: a threat to earth that could possibly end human civilization, main character(s) will have to stop it but overcoming that obstacle will be impossible when demons get in their way, will heaven help?

sorry im not good at writing english isnt my first language 

as you can see the story is still in development i honestly don't know what theme to add, help will be much appreciated :)

i also don't want to offend anyone's religion this is just fiction okay, i'm doing heavy research on these topics 😥