My current fort has been a major success, for the most part. I unwittingly became a barony, and shortly thereafter a county. Diplomacy with the humans and their vampire reptile man law-giver diplomat was short and sweet. Goblins were being dropped in the pit with the tame giant scorpion, who later inexplicably died and was replaced with a giant leopard. My population had hit over 200, and I was preparing a special room to capture the forgotten beast in the caverns. About half of my external wall was built, which I hoped would allow me to survive goblin sieges without having to make everyone run indoors and have casualties when they decided to ignore me to drink from the river instead of the well.
Unfortunately, I didn't have a heck of a lot for the dwarves to do, so there was this eternal party going on at the statue near the entrance, and they were getting really, really friendly with each other.
And then the dragon hit. A long-named, fully adult dragon, ready to go all Desolation of Smaug on my butt. "Great!" I thought. "The spots the dwarves kept standing on when I was building the wall got filled in with cage traps, and a straight line to my fort entrance will bring this guy right in there! Then I can craft some particularly absurd trap and really sock it to the goblins!"
Except he doesn't do that. Instead, it goes around the wall, making a beeline for the hives I had on a hillside. Then, unimpeded, it walks right into my fortress.
"Okay!" I thought. This isn't too bad! It'll walk right through those doors and into the cage traps I have for bigger goblin sieges! This isn't so bad! I don't need to open the drawbridge, because I don't want the weapon traps to kill it, right?"
It proceeds to dismantle the doors and the raised portcullis I'd just installed, stops a square short from the cage traps, and breathes right into the party hall. Half the fort population is annihilated on the spot, including my legendary miners. And the lever for opening the bridges. And most of the cage traps. (Wooden cages.) Then somebody shoots the thing in the leg, and it decides it isn't going to move for a while, instead repeatedly breathing fire into my fort from a safe distance. During this, several dwarves go instantly insane from having all their friends die. And not a single one is melancholy or catatonic. No, just a swarm of berserkers hampering the defense and recovery efforts. Luckily, half the fort seems to be a crack shot with a crossbow or expert martial artists, and the berserkers often had combat logs like "Urist McTeethgnasher assaults the kitten! Urist McCheesemaker punches UristMcTeethgnasher in the head, shattering the skull and tearing the brain!"
Anyways, the dragon then proceeds to step into a cage trap that had a metal cage, and the threat is over. 3 seconds later: "A vile force of darkness has arrived!" Okay, maybe the threat isn't over! They show up on the opposite side from the wall I have built, my trap pit is sealed by the bridges operated by the lever the dragon melted and pools of magma caused by dragonfire are preventing me from rebuilding said lever, the doors and portcullis are gone, the cage traps have been disarmed, and almost the entire population is too busy starting fist fights to fix anything.
I managed to get some dwarves to dismantle the bridges, so hopefully that will slow the goblins down a bit, allowing me time to restock the cage traps...