I don't know how I managed it, but somehow when I was constructing a staircase, I left a big hole in the floor that opened up into the top of a cavern, and didn't notice. The only real impact was that from time to time a bugbat would fly up and wander in, and I would find a loose bugbat mucking around in the lower levels of my fortress.

They were down in the wild and wooly cavern-adjacent part of the fort, with the metal shop and animal cages, and they didn't even seem hostile, but I still didn't want them pestering my dwarves. I set up some cage traps, and by the time I'd figured out what the staircase issue was and fixed the hole, I had a bunch of bugbats in cages.

So, what's good to do when you have some stuff on hand you're not familiar with? Start playing with it and see what it can do. I set up a room for the bugbats, started taming and training them, and learned that apparently what they can do is fuck, because in very short order I had an absolute shitload of bugbats.

A little while after that, I had more than that. Way too many. If I had had sense, I would have just opened another hole into the cavern for them and let them rejoin their natural habitat at this point, but I guess I felt responsible for them or something, because I kept training and breeding them long after it had become clear that (a) they were useless, and (b) I had more of them than I could ever conceivably need for any purpose, even if they had had a purpose. I started slaughtering them, trying to get a handle on things. All that happened then was they got loose. They would escape when some dwarf that was hauling them for slaughter would get distracted, or one would leave the room when the door opened to take out another. They started fucking and making unsupervised pups out in the main fortress. Bugbat pups became a frequent feature of my halls and stairwells.

Things were busy and they were slippery and numerous, and it was hard to make time for the level of attention it would have taken to really address the issue, and they were pretty much harmless, so they stayed as unwelcome but tolerated guests. But over time they became a menace. One of them had an altercation with one of the fortress dogs and injured him, which pissed me off. And then, there was an incident when the poor bastard who was assigned to train the goddamned things had some sort of bad interaction with one of them, and tried to abandon his task and leave the bugbat room, but the room was so stuffed full with upper and lower case "b"s that he couldn't manage to push his way through them to the door, and I thought through the screen I could feel his rising panic as he realized how badly outnumbered he was, and that some of them were barely trained, half wild, and that the tenor of the room had changed and he was totally alone, and tried to control his terror as he struggled harder and harder to reach the door through the crush, before they all fell on him at once.

I decided to kill them all. It took -- no joke -- many years between the firm decision, to when it actually came true. The issue was that there were so many that it was impossible to give an order that would apply to all of them, which could be carried out in full before they had made more pups and created a population to which the order didn't apply. It was tedious and difficult to almost a mind-numbing level to even find them all, or issue any order on all of them, never mind the time involved in actually carrying it out, or the new ones that would arrive in the meantime. I built two butcher shops and assigned multiple dwarves to full time bugbat-killing duty, severely annoyed that my labor force was having to make this a full-on fortress priority instead of some more productive thing they could have been working on, but the time for taking the bugbat issue lightly had come to an end.

As with so many things, the end came a little anticlimactically. I morosely went to pore over the list of bugbats and re-designate the new pups for slaughter as I had done so, so many times before, and found no bugbats. I found myself like a prisoner who's been set free, disoriented and blinking in the sun. What do you mean, no bugbats? My dwarves can get back to work now? No rotting bugbat corpses in the butcher shop because someone was too busy to take care of it in time? No lower case "b"s blocking the door I need to close? What the fuck do you mean there aren't any bugbats?

It didn't even make me happy. I think I was still too irritated about the whole debacle to even reassign their keepers to any other duties right away. I simply didn't want to deal with it. No bugbats. Great. Thanks. Wonderful. Can I go now?

So. It was in the early hungry days of my fortress, when the military is half a dozen guys with wood crossbows who can't shoot, when everything is big mining and grand plans and challenges of lacking basic infrastructure, and no unpleasant memories walled off forever in some secret corner of the fort. That, and realizing there's some shit you're out of now, that you forgot to worry about. Great days.

So in those heady times, the arrival of migrants is something to be celebrated, back when it's vital work force and before it turns into "Jesus Christ where am I gonna put you guys." So when a little band turned up I was happy to have them. They were a little family, I think 3-4 adult dwarves and one little girl, and they were all weird.

I have never before, or since, encountered a dwarf that on their personality sheet "dreams of bathing the world in chaos." No creating a great work of art, no raising a happy family, just chaos. Another one dreamed of ruling the world. They also, some of them, had incredibly impressive stats in some unusual areas. Well... dwarfs are odd. Whatever. Here's your tools, you're a carpenter now, make some bookcases, I hope you won't be a problem.

I cannot remember if they did anything alarming before the incident, or if the general unease I felt about them was just because of the chaos thing, but I definitely had a feeling of unease about them. And then, out of nowhere, there was combat.

What the fuck. Why is there combat? I paused, began flipping around, and was met with a confusion at the entrance to the fort, and eventually pieced it together: A hunter had killed a monkey, and was bringing it back to the fort to turn into monkey roast, when one of these fuckin guys brought the monkey back to life. The reanimated monkey corpse then bit the hunter, which had made him alarmed and unhappy, and the mere fact that it was back alive again was horrifying several bystanders.

Once I figured it out, re-killing the monkey was easy enough, but after that point the new guys were solidly on the shit list. I tried to evict them from the fort, which for some reason didn't work, and lacking the mental bandwidth to put proper attention to it I just put one of those little mental I-don't-like-this asterisks on their names and hoped they wouldn't do anything else weird.

Then, their little leader got himself elected mayor.

Fuck this. This guy has to die. I don't know what their plans are but they are not aligned with success for my fortress.

I had learned by this point that the obvious solution, just taking any weapons away from him and putting him in a room with a bunch of axe guys and hitting "K", was likely to lead to strife in the future, especially if he was mayor. But. I had a brand new water trap. It was a massive cylindrical tank, about 120 feet in diameter and several stories high, with a long corridor winding around its circumference, and a big gate that could click open and connect full tank A to enemy laden hallway B, and other gates that could slam shut at both ends. This thing stayed as the main defensive feature of my fortress for decades, and rarely let me down, but at this point it was absolutely brand new, and untested.

Well, guess what your new role is, monkey guy.

I put a desk and chair at the midpoint of the hallway, and told the new mayor that that was his office now. In pretty short order, he went and sat down, eager to get to some work I guess.

Soon after he sat down, the gates, far far away at each end of the long hallway, slammed shut. He would have heard an eerie, total silence for a while, in the empty closed off hallway, and then in the distance a rumble like a distant train, but getting louder...

The remainder of the band I was able to evict or kill. I hesitated when I got to the little girl. She, too, dreamed of bathing the world in chaos. But she also was 9 years old, and she clearly hadn't done anything. I decided to simply let her be to make her way in the fortress. I have to admit I was a little bit curious what if anything the chaos thing would turn into.

This was the close of the first chapter of my fort. It was the beginnings of decent infrastructure and effective defensive works, and the end of innocence and hopeful plans unmarred by DF's chaotic reality. I do not know if anything bad would have happened if I had let the little necromancer run my city, but I had a pretty good guess and no interest in finding out if it was accurate.

Courtesy of @otterX