“ Something lives in the fog in a certain region and travels with the fog. Kidnaps or kills, or is simply heard and 'felt'. ... fog is rising, heed the warnings the elders spoke!”
“ A small, primitive village has yet to discover fire, which is a good thing because there are highly flammable (but not otherwise dangerous) gasses in the air. The heroes, blissful in their ignorance, don't know that and think it a wonderful idea to show the locals open flame.”
“ The lengthy process to do something necessary or a magical scroll needed is inscribed on the other side of a great tapestry and can't be removed. For more fun it could be in the kings throne room. Try to hide in shadows with a 20*5 (yards/meters) monstrosity!”