Well, just need to get this right off the ol'beard... but there has to be some sort of (semi-realistic) conditions that, at most, prevent a player's fortress from developing.
As I've thought about it for some time, here is my current idea for an unembarkable location:
- The whole region is made of gem tiles. No soil, no stone, just gems. (At least until the magma sea)
- There is no water and no mud as well.
- There is no vegetation (trees, shrubs and grass) present in the map.
Why I think it is the hardest embark ever? First, there are no building materials. You can't make beds, doors, traps, barrels... anything other than gem windows or cutting rough gems. There are no food sources present on the map, unless one of two happen: either you have an elite hunting team and the roamers that enable the hunters' work (also, bolts would run scarse) or you bring along some egg-layers... which also means that, due to the nonexistence of building materials, nest boxes would also have to be brought at start.
Water, despite not being essential, it's needed for wounded dwarves not to die from dehydration. It would, in this setup, be needed to make obsidian which would be the only building material. Also, if water doesn't exist, there also can't exist mud.
Everything combined, smelting the sieger's armor seems like a good idea doesn't it? Well... unless someone had the audacity to bring a magma-safe building block for the magma-stuff, that plan remains frozen.
So, turning to the only thing that can save this fort: gems. Oh, and Trading. But here's the deal... most gems are pretty worthless even when cut. The only big value gems get are when encrusted, and as there aren't any crafts that are possible to be made voluntarily, this idea is put off for a while. So, a fortress would need to churn as many gems as possible in the first year just to purchase essential commodities from the caravans. So, more picks would need to be brought, alongside with enough material to make jeweler's stations and the trade depot.
This is all true until you reach the adamantine spire, where it could be used to make the magma-stuff buildings. However, a lot of fun stuff could happen in the meanwhile and after, which would endanger the fortress yet another time.
All in all, I think this fortress has a tonne of stuff against it ever becoming a viable place. So, this would be one heck of a !!FUN!! game.
Now that I have written this, what are your two cents on this?