I exploited the vermin-hunting behaviors of cats to bait all the zombies milling about on the surface into my drowning pit trap. They won't drown, obviously, but now they're safely sealed away in the drainage tunnel. I took advantage of this reprieve to send out a messenger to nearby holdings. I recruited a couple of merchants (glad to see that the 'useless merchant' bug has been fixed), bringing the population up to a grand total of 14 working dwarves. I also took the opportunity to make as much charcoal as I could before a new threat cut off my access to the surface again.
Unfortunately, I got complacent. A yak corpse that I had completely forgotten about reanimated. Before I even noticed any interruptions, it killed my Chief Medical Dwarf, Zon "Sawbones" Ralsobir ("doesn't try to get things done perfectly," and "sees the pursuit of knowledge as a worthless endeavor," aren't traits I'd want in my physician, but he gets the job done). As well, a macedwarf died in the fight to put it down.
But!
I had a few tricks up my sleeve... See, the old Captain of the Guard - "Deadfoot" I called him, on account of the nerve damage in each of his feet - he was brutally efficient at his job. All these years later, even in these more lawless times, the prisons of Saltcanyon are still full of the undead would-be thieves and spies so prevalent in the vast haunted jungle that surrounds the small serene valley these dwarves call home. And a few of those prisoners are necromancers.
After a little fiddling around with pit zones, fortifications, floodgates, and coffins, I sent the military to attack a necromancer that they could see but not reach. The first attempt just reanimated a bunch of pet skeletons. The second attempt yielded no results at all. But on the third attempt, ol' Sawbones shuddered and rose back to life as a Pale Hunter!
Sadly, I couldn't get lightning to strike twice. The dead macedwarf remains dead. I'm revising my setup to what I hope will be a more effective configuration should I need to resort to this again. For now, I'm forcing the dwarves to get some R&R and hoping that they can actually start forming relationships and starting families. Haven't had a single migrant in years. Need to get the population up somehow. Might have to edit the raws to make unicorns trainable for war. Send the dwaves out to free prisoners from goblin sites.