While, technically, Kropmork and Nahk are two different islands, they're basically the same nation (or stinking cesspool, whichever terminology you prefer), generally referred to as Kropmork-Nahk. Kropmork is more populated and generally populated by the upper and lower class, while Nahk is mostly reserved for mining mana crystals. Ruled by a Patrician who would make Machiavelli give up political theory and take up something like, say, painting, the nation has become a commerce giant. Kropmork and Nahk's economy specializes in trading, mining, and organized crime.
Practically every trade has a Guild. The Assassins' Guild is particularly popular among wealthy members of society who want their children to have a high-class, respectable trade, while the Thieves Guild, despite being legalized crime, is almost better at controlling crime than the City Watch... and let's not even get into the Seamstress' Guild, shall we? Let's just say that, in Kropmork-Nahk, there's something for everyone. If you don't get shanked and/or mugged, that is.
- Kropmork-Nahk was indeed inspired by the Discworld books, and is an anagram of the city's name from there. While some features are similar to what is found in the books, others are unique to the game.