Welcome Imperfectionist and Jannah! Yeah, I'd like to steer clear of the faith and basically have the lore loosely based off the legends, much like how Jade Empire was inspired by ancient china. It's a mythos I'm not well versed in, so I'm all for collaborative world building with everyone involved. An assassin I could see happening for either group, but a Djinn would be kinda tricky...unless I make them as avatars of the elements where people draw their magic from...

Edit: @Nug that's an awesome possibility that I'll allow!