I wouldn't exactly use the Crusades to refer to the idea (where muslims would then be daimons?), but yeah, it is fun. And it is indeed sort-of what Thalmarkin wanted/tried/did.
However, after each (good) invasion, most lands have turned rogue and only a few realms really survive. It's usual that after invasions a colonisation of sorts begins, reconquering rogue lands to start new realm, or recreate old ones (but perhaps in different regions).
