So I was under siege and tell my markdwarfs to fall back from the fortifications since a few of the goblins are elitebowmen. Well one of the stupid shits run all the way down into the cavern level at the same time a forgotten beast was approaching. I was too busy with the siege to notice at the time. I have 6 cave in traps in a row. Its super redundant. I can take out 6 things in a row before I have to reset. Of course the FB is still in the first room trying to break open the door, waiting for me to drop the roof on his head. The idiot markdwarf goes in and duel this thing. Surprisingly he does well. The beast is heavily wounded, but it is breathing a dust attack. but it doesn't seem to do any damage. He has no apparent injuries because being unconscious.
So I finish mopping up the siege with my 6 military without any losses. and I remember about that FB. I expected him to have broken through several doors by now. But I saw the markdwarf laying on the ground next to him still in the first cave-in chamber.
Instead of sacrificing him for his stupidity and killing both with the pull of a lever, I send a single sword master to go finish it, since it didn't seem to be too dangerous. It went down without much effort, but my swordmaster and a few civilians going in to clean up are exposed to the dust attacks. They all go unconscious, but not before the FB is killed. I think I made out pretty well. then while checking some injuries in the hospital. I go to the health screen to see why they are unconscious and discover all of them have lost their vision. I knew it was too good to be true.
They all recover quickly, but the vision loss is permanent I think. Later on I see a report of the swordmaster sparring a rookie sworddwarf. The sword master is missing everysingle attack and isn't blocking any of the rookie's attack. He is going to be useless now.
It would have been better to kill the markdwarf with the cave-in trap. Now I have a half dozen blind morons.