The further you went into the region the less hospitable it would be(i.e. more bears, wolves, and more aggressive, different creatures that have adapted to that climate, less vegetation besides firs and maybe some other hardy unique plants).
The key aspect about this area would be the climate, it would be more stamina draining as you entered it, most actions would use up more stamina when you're outdoors in the cold(more caves to balance this out as they can serve as checkpoints and shelters...unless they're already occupied
). There could be snowstorms or blizzards that would reduce your line of sight similar to night, except it would be white, as well as reducing your walking speed. The farther you ventured into these regions, the higher the stamina drain penalty would be applied.In order to brave this new environment you would need to be prepared - which means clothing. The introduction of a new stat on clothing called "Warmth" could be implemented where the more "Warmth" you had, the less stamina would be drained from this rough environment(i.e. wearing a linen shirt and trying to chop a tree would drain a lot more stamina than if you were wearing some bear fur).
Then lastly there would be the incentive, the reason why players would ever want to travel to these harsh places. I would suggest that there would be game particular to this region for example seals, walruses, penguins, polar bears...maybe an occasional beached whale event near a large enough water mass as well as ice fishing, as well as more mine locations could provide enough resource-incentive.
I understand that this is a big suggestion, and I understand the probability of it ever being implemented, but I think it is better to suggest than not to.
