Well, so I hadn't played before, just watched a few tutorials.
Anyhow, I got a farm going, dug down and around a bit and such, opened a huge cave by mistake (I had no idea how to close it). The cave let in some creatures (trogdlytes?) that kept attacking me, annoying. So first I tried to block it off with some walls, unfortunately my mason left himself on an edge he couldn't get off, and although I saw him there, I figured he was just lazy. He ended up starving to death.
There were two trade caravans. I stole all their things by deconstructing the trade depot. Seems like a good idea? Free stuff! A dwarf child went insane because he couldn't construct an artifact, and I had to send a spearman after him. The battle report so nicely described it, the spearman dealt with this poor child by striking off his arms one by one, so that they flew in a nice arc.
Anyhow, maybe I went mad. Harassed by trogdlytes. But I got tired of the dwarves so I deliberately caused a small cave in, diverted a flood into the fortress, stopped food and booze production and moved the refuse pile inside (and broke open all tombs). On top of that, a giant cave spider slaughtered half of my dwarves down in some dark cave.
So, in the midst of small children going berserk and starving to death and the purple miasma fumes my dwarves slowly died. The bedrooms were all filled with corpses, miasma spewing out like a chimney through my entrance. I had two remaining survivors (one of them slept next to the corpse of his friend, and was haunted by the ghost of two others nearby). I figured they'd all die soon... A cave alligator had broken in as well and was tearing up my pet animals, spraying the walls with blood...
But no... a group of about 30 migrants arrived. To this scene from hell reminiscent of event horizon, with dead and rotting dwarf corpses throughout the fortress, no food, no booze. Which cruel game would send more dwarves to die to this.