What makes an adventure "fit" Shadow World? How would you say that fit differs from other settings and systems?
Interesting question. Kulthea, to me, is a high-fantasy setting. There are flying ships, dragon-lords, nigh-world spanning organizations, and some very extreme/unusual locations, as well as a seriously high-level meta-plot.
But, even through all that, there are those "normal" places: Villages, cities, towns, plains, forests, mountains, etc.. The combination of all these factors make it so that just about every type of adventure can be had. One week you can be tromping through a dismal marsh looking for the lost temple, and the next be caught up in a murder mystery in a large city.
To make an adventure "fit" Shadow World (or any setting, for that matter), just incorporate Kulthean locations, peoples, names, etc. (Of course, to make an adventure fit
The Forgotten Realms, you don't use Kulthean information....
)
Plus, the old AD&D adventure,
Expedition to the Barrier Peaks fits here much better than in
The World of Greyhawk - the world is connected to the original (best
) Spacemaster setting.