I had this huge, wealthy fortress embarked in a zone with almost no enemies (besides the eventual forgotten beast or rampaging badger boars), I excavated to the lower levels to reach the magma and (praise the gods!) the adamantine tubes. Yet when I was excavating one, Fun is almost unleashed, which I managed to stop by constructing a floor tile over it.
So there was the richest fortress, about 220 in population, soon I was able to buy an entire caravan with a couple adamantine crafts, the Dwarven Queen arrived and set the fortress as the new Mountainhome. An army of 50 adamantine-clad infantry men trained day and night and were capable of easily killing several forgotten beasts, some of them getting processed at the butcher shops, while the engravers recorded the events on the fortress walls for future generations. A golden colossus was built on the outside for wonder of travellers and merchants, since gold veins were around and massive quantities of gold bars were smelted on the magma shops.
So...
Lack of enemies made things slow after a while, so I decided to unleash the contained hell on the pierced adamantine tube. So I amassed my forces by the floor tile and set it to be removed.
Meanwhile...
Queen- "Meh, slow day as always, I wonder what's happening on the magma foundry... hey! somebody set that floor tile on the forbidden place to be removed! well I guess its something important so I better take charge of it..."
Not to be said, poor lady Queen was slaughtered quickly by a fireball. The army wasnt enough to get those demons down, and when one was killed it would probably explode to kill more dwarves. So the fortress was quickly decimated and abandoned, I will visit it later as an adventurer and check if demons are still around...