So like, my 20-dorf strong fort was under continuous sieges, losing axe dorfs like you wouldn't believe (one multi-legendary axe lord managed to get herself shoved into a lake and drowned, only managing to kill 2 dark stranglers), and after having many foes clog up the weapon traps, i decided to make a panic move and use DFHack to magma the weapon traps (very effective) and start a controlled fire outside. Not long after, i learned that "immolate all" really does just that. I like to think that it was Armok dicking around, since DFHack also said "Praise Armok!".
After a world-encompassing inferno had passed (which conveniently enough killed all invaders), i was down to 9 healthy dorfs and 1 insane (from a failed mood). Another one went melancholy shortly after (unhappiness), leaving me with 8 unhappy dorfs. Miraculously, only one tantrum happened, and it only resulted in a thrown boulder and single destroyed bed.
This mass-death also resulted in 4 ghosts rising at the same time, who proceeded to haunt the rest of my dorfs. Fortunately, i managed to put them to rest via slabs and an immigrant expert engraver, before they made the others insane. I'm now back up to speed with 31 dorfs, but there are currently no trees on the map whatsoever, and i have a fey gem cutter who wants logs, and my stockpile is empty. :U (and the world is still partially covered in ashes from the fire)