Today's session had one of situations that I think are awesome that would have lost a lot of impact if scripted.
The catalyst was classic; the PC that was on watch while the rest of the party was asleep actually fell for the "Look over there, its a shiny" and wandered off to go see what it was and confirm why it was so shiny.
Now, this sort of thing generally leads to something between innocuous chicanery or instant death, depending on what the shiny thing actually is. Today, it left the sleeping party prey to something that had been following them around for a session or two that they had not been aware of; an invisible stalker.
So it quietly creeps up to group, and finds the smallest outlier - a spunky gal named Esther - wraps its hands around her throat and starts strangling her. The stalker manages to get its fingers around tight enough to prevent her from breathing at all, or making much of a sound. Esther's player tries some pretty clever stunts to break free and/or alert the rest of the party, but the dice are just not on her side today.
I keep rolling high for the strangulation damage, and I realize that this scenario would be a really awful way to die. Esther is kicking and fighting to no avail, being suffocated by a murderer that she cannot see, and her best friends in the world are literally no more then ten feet away and completely oblivious.
Hey, no one promised that dungeon crawling was glamorous.