And one starts to ponder why there aren't wars.
Even historical wars might be more clutter that the world can take, since even as back story they can draw attention. . . .
Hmm. . . hmm. . . hmm. . . oh yes, I've already got the spell. Perhaps Mercurio, capricious as he was, was nevertheless not unique. He just cast a big version of a spell that makes it much harder to invade a place than to defend it. Above and beyond the usual problems of invasion, that is. Which means it just slithers neatly into the world-building. . . .
Perhaps I can have a rebellious lord trying to compartmentalize his land with that spell. It will give me an excuse to info-dump and the world a little background.
It can be fun, finding things abruptly fitting together. 0:)