Another unsuccessful fort was embarked on ~1/3 evil biome, and from there came the skeletal wolves and horses. The militia was hitting their stride and doing fine clearing them out until one horse started getting lucky shots that killed or incapacitated 6 out of 8 soldiers. So only 2 remained when the goblins walked right through my poorly considered security while almost everyone was holding an anniversary party at the meeting hall. The expedition leader was the only one willing to do work, so I had him finish the shaft to the black citadel and pull the upright spike.
This was v34 when hell was so leaky that my adventurer had already enountered random demons, and slayed demon masters posing as gods. But I didn't see any demons topside, only random skeletal animals, terrified goblin raiders, and an insane farmer. Down in the 3rd cavern I started running into demons, but fortunately they came at me singly. I found the dead expedition leader and took my first adamantine weapon, a long sword. I took it all the way down to hell, cleared out all demons, and went back to the top.
Then the demon horde that should've spawned finally did, and began wiping out any remaining living beings. The demon master that appeared with them was as tough as the ones I'd fought before, and fortunately her squad had scattered to do their own slaying, so I didn't have to fight more than 3 at once. I doubt I would've been able to fight the whole bunch of them banded together. But I made it with all my limbs and no syndromes, and continued on my adventure.