So, I was just with a group who got clobbered in the Brecht mountains. I'm not putting this in the bugs forum for overpoweredness, because even though it's close to the starting area, I think the lack of road and general atmosphere should be a bit of a warning that this is not an area for low-level characters. That said, how about a "danger, treacherous mountains" sign? Or maybe some flavor text upon entering: "the mountain chill begins to seep in to your bones, and you can hear the distant punding of large feet" type of thing?