All PCs would be members of a circus traveling the world. Select an occupation from all circus performers and a species from species. No humans, no mundane characters.
Some facts about the Grand Spectacle:
At least one member of the circus (not necessarily a PC, but could be if you want) is an alchemist seeking to complete the Great Work.
The circus has an dragon's egg that has not yet hatched.
The circus is plagued by conflict with a group of redeemers and their religion.