With that in mind, I've decided to strip the Grand Duchy (It's not a kingdom! :P ) back to it's original presentation, then examine the later material and suggest some of my own ideas for using it in a campaign.
We'll start with module X1: The Isle of Dread. Along with what is essentially a slightly expanded version of the Expert Rule Book's map of the Known World and nearby island chains, a brief paragraph summary of each nation and region is included. For Karameikos, it has this to say:
Grand Duchy of Karameikos. This part of the continent is a wild and unsettled land claimed by Duke Stephan Karameikos. In reality, little of the land is under the duke's control. Large areas are overrun with monsters and hostile humanoids.Following the brief "gazetteer" of the Known World, there are a few brief notes on climate and weather. Given Karameikos' relative position to the countries mentioned, I think it is safe to assume the statements about Thyatis and Darokin would apply to the Grand Duchy as well. I've bolded the relevant information for reference.
Weather & Climate(1) I make the assumption that in Karameikos, the strip of coastal lands, one or two hexes wide on the X1 and Expert Set continental maps, where there are no forest map icons, is mostly rolling plains, small hills and grassland, with farmsteads and ranches scattered about, most notably near the cities of Specularum, Luln and Kelvin, with a smaller farming community around Threshold, as shown on maps of that city, found elsewhere.
The general weather patterns of this part of the continent move from west to east. Hence, much rain falls on the western edge of the Altan Tepe mountains, while little or none falls on the Alasiyan desert. The warm offshore currents near Thyatis and Minrothad modify the weather somewhat in the south, making the climate there similar to the Mediterranean.
The southern farm lands are extremely fertile, due to a thick layer of rich ash from the ancient volcanic hills. The farmers here have discovered better ways to grow most crops. The heavily irrigated and terraced gardens of the southern farmlands produce more food than any other area on the map.(1)
The climate in the Thanegioth Archipelago is tropical, similar to the Pacific South Seas islands (Oceania) and the Caribbean. The climate south of the Cruth mountains (running west to east) is moist and temperate, with mild winters. The climate of Darokin and Glantri is warm and sunny, similar to that of southern France. The climate of the Ethengar steppes is mild in the summer, but cold and bleak in the winter; like the Russian steppes around the Black Sea. The climate of the northeastern coast is wet and mostly overcast, similar to that of Denmark.
All in all, this bare bones bit of information makes Karameikos sound like a great locale for adventures using the "standard" Euro-fantasy medieval to early renaissance D&D genre. Consider also the fact that every major terrain type is present in, or fairly close to, the Grand Duchy. Forest, plains, coastlines and mountains abound, and snowy, wintry locales can surely be found in the heights of the Cruth mountains. The vast deserts of Ylaruam are a short trek to the northeast, while the murky depths of the Malpheggi swamp lie just west of the neighboring Five Shires. With a major port such as Specularum, the tropical islands are within easy reach as well.
Speaking of the Five Shires, it's interesting that the homelands of the major Demihuman races are all close by as well. The Hin (Halflings) are direct neighbors to the west, while the Elves of Alfheim and Dwarves of Rockhome are both a short trip (across the neighboring human realm of Darokin's rather unsettled eastern wilderness) to the north. This makes it quite easy to justify having all four of the standard PC races present in the towns of the Grand Duchy, rather than force the players and DM to concoct rambling backstories to explain what a particular character is doing there.
The Expert sets (both Dave Cook's and Frank Mentzer's editions) have some more detailed information on Karameikos and the city of Threshold, but I want to take this examination of the Karameikos subsetting one step at a time and not get mired in referencing too many sources in each post, so we'll take a look at those next time. Even if you stick with what we have so far from X1's map and map key notes, you could easily start to build a campaign, so to put it bluntly, everything else is basically just fluff anyway.