Talk about anti-climactic.
I had an FB arrive in the caverns, a towering quadruped of faint yellow diamond, breathing frost. he stomped around the land areas, then ended up in the lake right below where my up/down staircase opened up. I hadn't managed to hatch cover all the stairs yet (got distracted by two gobbo sieges). I suddenly get injury reports, and there he is, down in the lake, trying to hawk frozen loogies up at my dwarves. I'd made a well nearby, my dwarves were meeting there...so I quickly freed up the room and ordered them to burrows...
...aaaaand they were all stuck, because the frozen FB breath had created blockages. I had about 50 dwarves in there, too. So they all started blocking up, smashing together, like something out of a panic scene in a movie. there was a diagonal path around the frozen breath, but not all of them could get through. So I try having my miners dig out a path, but keep getting "Oh teh noes scary!" cancellation spam. Meanwhile, the trapped dwarves are flashing thirsty, and I was thinking back to the event a few years' prior where 3/4 of my 160 dwarves had died of thirst... the military obviously can't reach it and I was doubting they could kill it anyway..
Finally, it makes its way up and in (how, I don't know, it doesn't fly, maybe all FB's are related to Jason Voorhees and can teleport) and I send my military after it. While they're making their way down, one of my engravers beats on it with her fists, and a dog is chewing on it. The two of them manage some significant damage on it. Then the military comes in and..... it's gone. Dead after less than a minute of real time.
Aren't FB's made of diamond supposed to be super tough? I think that one was made of those plastic gems on cheap dress-up toys instead
Mind, most of my military is legendary Axe and or Hammer Lords in steel and bronze.
feel free to share your own anticlimactic encounters!