I am in a constant state of terror in my current fort. It's quite new (I'm still in spring), but the first season is always the most stressful. My embark is nothing short of god awful: no ore, no flux, 3 necro towers, reanimating, thralling, glacier, and also there is nothing but the mountainhome, so I can't expect many migrants.
Also there's a vault on it, which is probably an advantage because of the divine metal I'll eventually be able to exploit. Fighting angels (and quite possibly their reanimated corpses) sounds like a later problem, though. Still, it's interesting!
I've successfully tunneled into the cavern layer, and am creating my fort around it (I've got quite a bit planned out), but the caverns are rife with danger. The first wildlife I get is a blind cave ogre and a jabberer, the former of which my farmer got into a small scuffle with while exploring. He managed to scare it, somehow, and walked away unharmed. Later (still with the jabberer and ogre on the map) some cave swallow men and an undead GCS faced off (where the latter came from I have no clue, but I have very little of the northern caverns revealed). The cave swallow men won, but lost one of their ranks, all becoming zombified and then getting rekt when the jabberer wandered nearby. So it's been constant close calls, which is terrifying because the fort was not successfully sealed off from the caverns for all of them. Just now the non-obscure ways are sealed (there's still a small waterfront entryway, though the lake it's on isn't connected to the edge of the map), so the fort is finally somewhat safe.
Also, the cats wandered off in the caverns (they're safe) and a freak swarm of creepy crawlers drank all the booze. Damnit. At least we still have food, and barring that, we have horses to butcher. Looks like my poor dwarves will have to suffer water for a bit, since not dying takes more preference than making everybody comfortable.
Update:
The fort is going quite well. The majority of what I'll need is dug out, the undeadsplosion is only tentatively taking over the surface and caverns, and, most notably, a final wave of migrants was able to get into the fortress mostly unharmed!
The migrant wave was particularly terrifying, as all of the migrant pets got turned into zombie thralls. Two of the migrants bravely sacrificed themselves to get the others in through the entry hatch: one, a miner who was the last dwarf on the map, and the other, a peasant who also got thralled, yet kept fighting the thrall animals (minus one, who the miner fought). Sadly, both lost their lives (perhaps not sadly in the case of the thrall!), and the miner was knocked unconscious and was unable to escape after everyone had gotten in safely. Both went down fighting, and neither will reanimate: if nothing else, this is a testament to dwarven courage.
With the three migrants from the hardcoded waves (the second wave was stopped by a necromancer siege), this brings the fortress population up to 16, a much more reasonable number for basic operations. Unfortunately the fort is suffering from a crippling wood shortage, and so the new migrants won't be able to have beds until I resolve the problem. A risky endeavor into the caverns is likely, since I just need a moderate amount of wood to make beds, buckets, and the small amount of coal I'll need to get magma forges to the fortress proper. In this, I'm both upset and glad that I brought limonite ore with me on embark: I can make the minecarts I need since my embark has no ore, but the cost of the limonite stopped me from bringing more wood.
Speaking of ore, we have an eventual source of steel: the second dwarven caravan, which was unfortunately scattered by undead ice wolves (the last soldier brutally murdered all the wolves, but the caravan was too spooked to continue, or maybe all the merchants were dead). Should I be able to reclaim the surface (a goal that tends to happen in every reanimating embark I've ever seen, heh), or heck, even just sneak some stuff in, I'll have valuable goods the fortress might not otherwise be able to get. The fort does possess a breeding pair of sheep for the sake of not losing dwarves to strange moods that demand yarn (I actually "lost" my last challenge embark to that! My breeding couples both got broken up by yarn moods and then none of their kids wanted to marry), but leather, books, metal, and variety of gems will all be well received within the fort. Reclaiming might be quite difficult thanks to all the thralling dust smeared everywhere. Footwear seemed to protect the migrants as expected (and they didn't track any inside, thank armok), but that doesn't mean it's not dangerous.