Will every Terrifying region have evil weather (assuming that Terrifying surroundings are what you meant by "hell-on-earth")?
In any case, I am very, very happy that Terrifying regions will actually be terrifying instead of just being an evil region with [SAVAGE] wildlife, although that does render a significant portion of my mod redundant to to point of overkill :/
Also, monk12's post above brought to mind something odd...
'Evil' can be pretty subjective sometimes.
Bloody rain would certainly be creepy as all hell to, say, a human or an elf, but to a species that feeds on blood it'd be pretty much the greatest thing ever (assume that the blood-feeding species in question is itself benign, and that they have the resources to disinfect the 'rain' of airborne contaminants). In fact, if it weren't for the quasi-cannibalism factor involved in eating human/dwarf blood (I say "quasi" because it doesn't appear to be coming from an actual, living human/dwarf), I'm sure there are many real-life cultures who would go "Yay, free black pudding!" and set funnels outside before every rainstorm, or at least after they'd gotten used to it enough to not freak out every time the sky started bleeding.
Of course, this isn't really a problem; part of the fun of DF is taking fantasy clichés, applying them to an internally-consistent simulation, and seeing how such things would actually play out.
EDIT: Actually, I guess finding potable water would be tough in such a region.