Just found an embark site that has a very fast-moving evil cloud type that instantly zombifies any creature within it. Even worse, the fog-zombies' bite carries the sickness to other creatures. I'm going to attempt an embark and see whether I can raise walls quickly enough to hold back the clouds long enough for my dwarves to construct a dwelling of some sort. Hiding underground will be necessary at first, but is cowardly in the long term. Rather, I plan to establish a citadel that looms over the fog, raining doom upon enemies below.*
Starting out will be especially hard as well because the nature of the fog causes any animals that I bring along (often cats, war dogs, or fowl) to be a severe liability due to their tendency to bite and move about quickly. (Two war dogs on a test embark wandered into a cloud of fog and were able to zombify all seven starting dwarves in less than a day!) On the other hand, bringing no animals for food products essentially forces upon me the need for a vegan fortress! I've actually wanted to try such a thing as of late. Perhaps I can uphold an ideal of "prevent as much nonsapient animal suffering as possible within the fortress, but make up for it outside because goblins aren't nonsapient animals".
*Speaking of raning doom on enemies below, do the new parabolic arc physics permit catapaults to fire at enemies on a lower level?