Thieves' World is a dark urban fantasy Shared Universe created by Robert Asprin in 1978 and mostly focused on the city of Sanctuary. It drew in authors like Poul Anderson, John Brunner, Andrew J Offutt, C. J. Cherryh, Janet Morris and Marion Zimmer Bradley to contribute, and generated a buttload of books (12 short story compilations, 8 official novels, some graphic novel adaptations of the compilations and roleplaying adaptations from the likes of Chaosium and FASA) before it went on hiatus in 1989. See also the fan site.