Back when glowing pits still existed i had a greater demon rip my entire fortress a new asshole. A miner uncovered the bottom level of the pit, i didn't even know there was adamantine on the map until he dug into the pit and got instantly gibbed from the demon. I failed to secure the stairs so i assembled the entire fortress into a rag tag band of recruits with no weapons or armor. They piled into the hallway adjacent to the top of the stairs. When the demon emerged he blew a fireball at the crowd and killed 15 of the 20 dudes sitting there. The rest were injured severely. I only had about 10 dwarves left who were all raging and tantruming at the same time. I had managed to equip a few of them with weapons, which just made killing each other easier. After some slaughter the last three dwarves were all running around mad about their friends dying when the demon approached. He bitchslapped one into a wall, turning him into a fine red mist. Another got swiped by a fireball and had a leg severely injured. The final dorf was raging so hard he tossed his sword straight through the demon's head, splattering his black goo all over the dining room. After killing the demon he went over to the injured dorf, strangled him to death and then starved himself, ending the fortress. It was a ride while it lasted.