They were 40 humans, working together to build a monastery. They had foolishly copied the deep-delving techniques of the dwarves and sunk a staircase straight into the marble underrock. These were the first humans to pierce the caverns.
And fools they were, for they had forgotten about the pathing of creatures in DF and stupidly assumed that an 'up' staircase would block pathing from below. This single oversight writ their contract with death.
...
Half the alpaca herd was on fire by time I noticed a gigantic, firebreathing pterodactyl had attacked. I ordered the militia to engage, hoping their shields might give them a chance, but quickly they were all killed. The few survivors fled into the caverns, and walled off the staircase. The survivors lived another month or so, before a lack of water forced them to dig out. That was when the
other forgotten beast, a one-eyed webshooting crocodile, appeared out of the fog and decimated the entire surviving colony.
At this point I was ready to concede, but there was one injurerd dwarf up top. This dwarf had actually been stuck in the hospital for many months before the attack, and I sort of forgot about their existence. Well, during the chaos they somehow managed to avoid the pterodactyl's flame. In fact, the pterodactyl had occupied itself with destroying all the cellar doors, and so this final dwarf was able to wall in the dinosaur and end the threat.
So, in perhaps the oldest tradition of Dwarf Fortress, I will now attempt to survive with this lone dwarf as a hermit. There are far too many bodies littering the monastery grounds to live there any longer, so I've burrowed him in the northwest and begun to construct a lodge. If he doesn't go insane from the numerous haunting ghosts I just might have a chance to hole up and wait for migrants. Then I can think about cleaning up this mess...