>>8700
>unicorns
heh, it's your world your choice. Trying to autisticly resist googling the etymology of unicorn in a attempt for some harebrained half justification hidden in some obscure meaning.

>So, here's an interesting twist ... the ponies in the heartland still have magically-appearing cutie marks. But the magic doesn't 'spill over' or through, the mountains.
Knew it. Not that I knew this detail, but the whole magic being reduced/demythizied thing.

>Except I haven't quite decided why more of these farmers don't go back up over the mountains, although maybe I can guess why they don't come back. Any pony with enough gumption and curiosity to get through the mountain pass find a whole world worth staying in, and possibly only tries too, because they have a lot of negative memories, emotions, about their life back home that they just don't go back to say "hay, guis, there's still real magic over there!"
The journey should be really dangerous. If the peak of the mountains have a lot of K2 sized monsters and the farm ponies aren't too advanced and the heartland ponies are only magically advanced you can still justify it. Think of the old adventure fics from 2011-2012 when ponies could stumble on a advanced and completely separate civilization and culture just lurking around the corner somewhere too. Even if you have some sprinklings of industrialization you can make that work and justify it.