So I desided to make my new fortress with a twist, it must be 7x7, 9x9 if you count walls, everything must be built up/down in that area, I could quarry stone, hunt, channel liquids, etc. outside but everything else must be in the... Narrow Fortress.
Skip ahead a year or two and I have ~40-50 dwarves in a tall tower, most food comes from a 1 floor turkey battery farm with the rest coming from caravans, no wood, coal or lignite has fairly effectively brought the fortress to a standstill, more important uses for the wood from the caravans always came up and some bad decisions led to the channels that were supposed to be for magma filled with water and all the miners dead, in short the millita was lucky to have some low quality iron maces.
The beginning of the end started with the second were-mole attack, the previous one ended quickly and quietly with two deaths but no injury's otherwise. Not so with this one, lots of deaths, lots of injurys but nothing fortress-crippling, the wounded go to the hospital floor and pretty much all of them survive. One month later when the last of the were-moles, 9/10ths of my dwarves, most of the human caravan and any other once living things unlucky enough to be nearby are dead a forgotten beast announces it's self, it goes through a few of the last dwarves as it goes up the stairs until it meets my last able bodied dwarf, a master marks-dwarf, and the last of the caravan guards, after that spectacular battle which I did not see dew to the fact I had earlier given up and was browsing TV tropes the forgotten beast was the only serviver. Dispite it having far more broken bones than unbroken the forgotten beast, a 3 eyed web spewing partridge, crawled down the stairs and, mustering it's strength, heroically broke a limestone door.
Then some migrants came, visions of them beating the mortally wounded beast to death and then the master bowyer that came with them supplying a crack squad of marksdwarves fighting off any and all comers swam through my head. Instead they got stuck in webs for the beast to pick off at it's leisure. In the end there was 2 unconscious probably tyflopónthropic dwarves and the only surviving immigrant, a baby.