When adapting a famous horror novel such as Stephen King’s The Mist, it’s important that you cast your leads well. Spike’s new TV adaptation, for instance, has scoured the land, and yet, it still doesn’t have a casting announcement for that all-important role of “the Mist.†Will it go to the steely fog from the fields of Ireland? That upstart dew from the Brazilian rain forest? Until then, we know this: Six Feet Under alum Frances Conroy will star (co-star, really) as a “modern ecological martyr†named Nathalie. We’ll have to see how the rest of the aqueous shortlist plays across from her in screen tests.