My skill in fortress management is not Legendary; I don't make ☼Masterwork☼ fortresses. But I am pretty good. I'm good enough that I've never actually lost a fortress, I've just gotten bored and retired them. The closest I've come is the time when I learned what a loyalty cascade is. That was a lot of fun, but it went slow and new migrants arrived who were untouched by it, and I knew that the fortress would go on... so I quit. Never before have I gotten to experience the fun of losing. Until, as you've guessed, I made Basementsieged.
Part of my success comes from my caution when picking embark sites. Usually no aquifer, almost never evil biomes, and I've never made a fortress with a tower nearby. Well, I was reading through the first incarnation of Necrothreat, and it sounded like so much fun I thought I'd give Dwarf Fortress another go (I hadn't played in a long time because I had become bored with the game.) I made a new world and looked through the Dwarven nations in Legends Explorer to find one I liked - and, lo and behold, what a gem! "The Fortress of Amusement" That's exactly what I was trying to create! Also the current queen was a drunkard. I was disappointed to see that the kingdom wasn't at war, and never had been, and was also pretty large... but oh well.
I looked around for an embark site near elves, because I felt like going to war with them. I found a site in the mid-north on the western continent in an Untamed Wilds environment (!FUN!), an aquifer (oh well), and every kind of neighbor you could ask for: dwarves, humans, elves, goblins, and a tower! That excited me because, as I said, I'd never embarked near a tower before.
In preparing for embark I assigned two dwarves as miners and gave some basic stuff (woodcutting, growing) to the others, leaving one as hauling peasant. I planned to dig a massive, beautiful fortress. Instead of stocking up on nest boxes and ducks like I normally do, I just got a ton of rum, meat, and seeds for plump helmets and sweet pods. Then I went to name the fortress. I ran through a bunch of names, but didn't like any. I have trouble naming fortresses so I said to myself, "Whatever the next random name is, will be the name of this fortress." The next name was Basementsieged. Perfect! Sounds like !FUN! will happen there!
I had no idea how prophetic it was.
Basementsieged did not last one year.
Upon embarking I started digging into a hillside. The farm was up quick, and I decided to dig down into the aquifer to deal with it. I didn't make my usual all-purpose stockpile inside because I wanted to wait for my great storage rooms to be finished. My miners didn't encounter any water, so I told them to keep digging... ok, some more... maybe ten more levels?... OH **** CAVERNS! I immediately blocked off that stairwell and saw that spores had been released and were coloring my upper level. Later on my miners told me they found the aquifer, and I understood the situation. My embark site had two biomes, one flat with more trees, one hilly with fewer trees. The flat biome had an aquifer, and the hilly one didn't. My great store rooms were on the first quifer level, so some of them got cut short. My great hall was on the level above, and to my dismay I saw that it was half soil. I was going to engrave the whole thing! Oh well. And then mushrooms were growing in it... guess I'll call the inn/tavern Mushroomhall!
In early summer (I think), still pretty early on, I got an event message saying, "The dead walk!" I was under siege by about eight undead, mostly dwarves, but with two elves. All of the dwarves had names, but no professions, and the elves were both warriors. I had no military and no migrants, so I called all of my dwarves inside and started blocking off the entrance. But Urist McCarpenter was outside getting logs! In the end I couldn't bring him inside in time, so I put him in a military unit and told him to stay put. The zombies killed him.
Now I had six dwarves. Only the food supplies had been brought in from the wagon. We had no wood, and I wasn't going to brave the caverns (in hindsight I probably should have). We had a farm though, so we wouldn't die, and work continued more or less as usual. It was at about this time that I realized I had been put under siege while hiding in my "basement".
The store rooms were dug out, as was the great hall. We had plenty of drink and were now stocking up on plant food, while still having plenty of leftover meat from embark. But we had no wood, which meant no beds. I waited for migrants and none came. A season passed. I decided to move the meeting area into my great hall once it was finished, so I comissioned a stone table and got rid of the old meeting area. In the new hall, I made the inn/tavern Mushroomhall as I had planned. And then, to my surprise, a visitor almost immediately showed up! A human axeman appeared at the edge of the map. Oh good, maybe he can kill the zombies!
Nope. The end of that combat log showed the zombies all punching his head until it exploded into gore.
I lost a total of eight visitors to the zombies, but not a single zombie died. I don't know how to kill them. But I had a plan. I'd atom smash them! I dug a long-ish hallway near my barricaded entrance, and constructed two bridges in it (it was too long for one). I wasn't sure what to do about what direction they raised, since some part of me thought they might take longer to go down a wider hallway (2 Urists without a raised bridge), so I decided to make them both retract. Anyone who knows more than I did at the time knows that was a mistake.
I made a lever for the bridges in my hall and had all the dwarves gather around it in a burrow designation. I was too tired to bother with putting them into real protection, and thought my bridges would destroy the zombies. I had my miners open the last walls at the end of the hallway and two visitors ran inside, and a cat which had somehow survived outside for months. The zombies were close behind. The two elven zombies went in first and were slow enough to give my dwarves time to pull the lever, un-retracting the bridges... and... nothing happened! Nothing at all! The bridges were back in place but no atom-smashing had happened.
The zombies made their way into Mushroomhall. My visitors and dwarves fought them, and didn't die immediately. However, within a few seconds I had only three dwarves left, and then two, and then one. And then there were none.
And I had so much fun!