Considering there are two threads actively debating the philosophy of setting design, that got me wondering: for those of you DMing, what setting do you play in? How much of your setting is homebrew, and how much has been shamelessly "borrowed" from published material?

Personally, I'm running a game for D&D 5e set in a homebrew world called Nyth: at some point in the distant past it may have been part of the Forgotten Realms (or other generic fantasy analogue), but a magical catastrophe splintered a continent and cast the shards into a realm of pure chaos. These shards range from a few feet to hundreds of miles in diameter, and Nyth is one of the largest. The party's homeland uses a map of the Nentir Vale with the details changed... And most importantly, the common folk know nothing about magic: they hate and despise it and its practitioners, so wizards have to be careful about casting flashy spells lest they attract a lynch mob.

Tell me about your settings!