[@Invictus]Alright, that's a lot, so here we go:
Magic: Haven't entirely decided yet, I'm leaning towards incantation along with somebits of faith-esque (think Constantine). There will be Alchemy, but that's more science than magic

Groups: We'll see where the story goes, I wont require us to all meet up, but it would be nice if some of our characters met up

Artifacts: As in magical objects? I mean, there are items with magical enchantments, and there are objects of legend, like the Sword of King Arthur, the Armor of some Famous Conquistador etc. but there aren't like a widespread collection of cool ancient objects. 

Demons and Co.: Demons actually do have a hierarchy, which I'll get to when I put Demons into the bestiary. The angels are a bit less detailed, since they just take less involvement