The misted lands, located from -645/747 to -664/765, seem to the casual eye to be a big, dormant patch of mist. They aren't like the HOC, expanding as units are sent to it, or like the fortune teller, shifting place every day. They don't appear to be man, elf, dwarf, or orc-made, like the fortress of shadows, the steamtastic brewery, or the temple of knowledge. They are probably the least interesting of all of illy's know mysteries.
However, if we take a closer look, we see odd things in the mist. For starters, every misted square has the option to harvest and send resources.
Secondly, some "bleak mountain" squares stick out of the mist, while others do not. The ones that do stick out have different resource configurations than the ones that don't.
Thirdly, and possibly most importantly, there are two sets of three mountains that stick out prominently from the mist. They are located at -632/755 and -639/760. The second of these mountains is the more interesting one, as it has a resource distribution of 5/5/5/5/5.
Lastly, the plains square at -634/752 has a resource distribution of 1/14/3/2/5.
What can we gather from these clues? I think that in order to solve the mystery, resources must be sent and harvested from all the extruding bleak mountain squares. There are probably other steps as well, however I can't think of what they might be, given the clues presented. This is certainly a complex mystery, and may also be a dangerous one. Who knows what is lurking beneath the mists?