I've gotten this idea of writing a fantasy novel which takes after Full Metal Alchemist and the alchemic games of the Atelier series. Problem is, I'm more of a sci-fi writer than a fantasy writer, I like both genres, but when it comes to writing, sci-fi comes more natural. I don't even know where should I start writing from. Do I need to invent a whole new world with its unique people, races and languages? Or can I stick to a mirror world which takes after our own, but it isn't exactly the same (pretty much like how Philip Pullman did with his His Dark Materials trilogy)? If I choose the latter, do I need to be faithful to reality when describing cities like, say, London? Or can I invent a totally different London, but keep the name? I'm really (and I mean, really really) bad at naming places and inventing artificial languages, so the idea of inventing a whole new world kinda scares me. Also, do I need to have knowledge of demons, and creatures? And of magic and things like that? I was thinking of writing a steampunk novel set in a XIX century-like world.