Halo franchise, and the studio investigated a ton of options ranging from pure fantasy to hard science fiction. In the end, they picked a blend of the two which would later become Destiny.
According to Bungie design director Joseph Staten in an interview with Official Xbox Magazine, "We thought of a good handful of other genres as well. We've had a pretty long pre-production period and we explored everything from straight-up fantasy to something a little bit more modern to many, many other things as well."
"Ultimately we gravitated towards this mix of science fiction and fantasy because it gave us this freedom," he went on to relate, "You saw small things like the prevalence of cloth in the game, a lot of characters have capes or cloaks and the combatants have cloth as well. Fantasy brings us this texture that we can wrap around sci-fi, which is really appealing, especially if you're an artist who's just been stuck making straight up space armor for ten years. A bit of cloth is very refreshing."
Finally, Bungie settled on a space opera, which technical director Chris Butcher dubbed "mythic science fiction".
Destiny is due to be released next year on PC, Xbox 360, PlayStation 3, PlayStation 4 and Microsoft's next-gen console.