Alright, so, I first started playing DF about a week and a half ago, and in that time I created a nice beginner fortress in a dolomite hill, with virtually all of my wealth from selling masterwork dolomite mechanisms. I didn't assemble a military, since I didn't really understand how to, and so when the fortress hit 200 residents and about 8-900000 in wealth, a squadron of goblin macemen killed about 140 dwarves. I guess that's what I earned.
Anyway, so I was watching the fun ensue, and many of the dwarves are just carrying on in the fortress, randomly venturing outside to get drinks (and then be killed by the marauding goblins), and I was just letting things take their course. Dozens of mindless dwarves rambling around the watering hole, dragging corpses to the corpse stockpile (where the goblins killed them), etcetera.
Suddenly, I get this message, which helpfully informs me that a minotaur has come.
Initial reaction: okay, the game is designed to make me lose. I knew that.
So, anyway, I unpause to see what happens, and to my amusement, the minotaur immediately starts kicking goblin ass. I don't know if anyone's ever played SimCity 2000, but when your city was on fire (and you were letting it burn like a pyro), SuperSim would come along and magically put the fires out (somewhat). This minotaur was SuperSim. It killed two goblins in about ten seconds and then walked into my fortress, where it killed a couple of random dwarves (who were hauling stones, naturally, because what would you do when your fortress is being besieged?). It got stuck in a hallway, putting the beat down on a fisherdwarf, who somehow managed to survive the ambush. Then, it wandered into a room with a gemcutter's workshop (and an unfortunate dyer), and I sealed the door behind it.
The siege ended right after the minotaur came to town (no shit -- it's a minotaur), and with him locked up, everything seems to be in order again. A few dwarves tantruming, but nothing aside from that. The fortress was promoted to a metropolis the year before, and its baroness survived the siege. Imagine my further surprise when the caravan from the dwarven civilization showed up and told her, despite the fact that the hallways are drenched in blood, there are corpses everywhere (the goblins killed almost all the animals, too), and that we literally might not recover, that they wanted to promote the colony higher within the civilization.
tl;dr: Goblin siege, minotaur appeared, killed goblins, fortress in ruins but now has pet minotaur, things are going back to normal.
Somebody tell me what the hell is happening, why this fortress is smiled upon by Armok, and what I should do next. What do I do with my new pet minotaur?