Once we knew that our protagonists were semi-devine bruisers vying for full-membership godhood, our thinking turned toward setting. Where would Demigods go to fight? What is the Demigod version of 3:30pm behind the schoolyard?
Early on, we settled on the notion of a whole planet having been set aside for Demigod conflict resolution. Demigods and their quarrels are very old, so this place would need to be ancient. It would be a place where Demigods and their minions erected monuments and temples to celebrate their past and future victories. As we pushed this notion further, both in time and in scale, we realized that millions of years of this sort of activity would result in a stone version of Trantor or Coruscant: a world completely encrusted by layers of vast, weathered ruins. How big could these ruins get? Well, they're made by all-powerful beings with eons on their hands, so they can get gigantic. We wanted nosebleed-level scale: a kilometers-high edifice on a mountain seems big until you realize that the mountain itself is the weathered remnant of an immeasurably bigger and older structure, which itself rests on countless strata of progressively older ruins. With a canvas that big, the possibilities for individual arenas are pretty varied. With each new level design, I think we've managed to raise the "oh shit" factor a couple of notches.
Then there are questions about the origins and religious traditions associated with the Demigods. We didn't want each Demigod to map to a specific real-world culture, but we realized that allowing religious iconography to influence our characters and settings would give them an authority they could never have if we attempted to create something out of the blue. Already, there has been much speculation about which country or which culture each Demigod comes from -- we've rationalized their resemblance to existing traditions by assuming that world religious iconography has grown from hazily-percieved glimpses into the divine realm. The Greek, Roman, Egyptian, Norse, and Hindu pantheons are all a result of the blurry Bigfoot photo phenomenon. Little bits here and there are uncannily close to the mark, but the reality is quite different. More than anything, this lets us come up with some seriously off-the-wall Demigods that we wouldn't be able to make if we were shackled to a list of existing deities. I mean, where do you find the Rook or the Unclean Beast in existing religions? I'm trying to imagine having to share a bus seat with an Unclean Beast worshipper.
There's one other fun question: if Demigod means "half-god," where are everybody's fully-divine parents? A lot of religious traditions tell stories of randy gods coming down to sow their oats, and we liked the idea that each Demigod was the product of a mortal-immortal coupling. The fun twist, though, is that these Demigods are all fighting to succeed a single fallen god. What makes them eligible to compete? They've all got the same dad! Which of course begs the question: what on Earth did the Unclean Beast's mom look like?
Maybe she was a total neat-freak and he's just going through a phase.