“ Minor Cultural Modifier: The culture believes, for the soul to leave the body, the corpse' eyes must be open. So any member of that culture takes care any dead body they find has its eyes open. Doubly true for those they kill themselves, for then the corpse will surely rise as an undead hunting him.”
“ 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.”
“ A terrible affliction spreads through the land: A disease, highly contagious, which makes its victims mildly ill, but then permanently paralyzes the vocal cords. Dozens of reputed cures and protections are sold in the marketplaces, which gradually grow quieter and quieter...”