Oathbound takes place on the world of the Forge. Eons ago the gods got together and locked away some persnickity deity and made 7 of his followers be in charge of the locks. The deity's prison is a world and the locks are each a realm under absolute control of one of the "feathered flock". (The followers had a bird-like theme, think the Raven Queen from 4e.)
Well, putting the deity's most loyal servants in charge of his imprisonment isn't the wisest thing, even if they are forced to maintain the locks (they are oath bound, you could say).

Eventually they realized that they could pull beings from other worlds to this planet. So they all start pulling in powerful heroes in hopes that they can eventually break the locks and release the imprisoned deity.
So, this is a world that has had adventurers and powerful creatures pulled into it for ages and ages. So there are cities and commoners, but since everyone is either an adventurer or descendant of one, the place is pretty jacked up. For one thing, everything is powered up - your senses seem richer, crop seasons are less than a month, everyone who is pulled get a boon or some sort. Etc.