I mean, what is your innermost, deepest, if-Freddy-Krueger-were-after-me-this-is-how-he’d-kill-me fear?
Lots of people are scared of heights, or spiders, or snakes, or whatever; many to the point of actual phobia. But deep down inside there’s got to be something much more fundamental. Something that fills you with existential dread to the point where it’s difficult to even imagine, much less articulate. It’s often a theme in our nightmares, although it doesn’t have to be literally played out there. Often a hint is enough.
For me, it’s immobility.
The thought of being trapped in my own body, watching the world go by around me, completely unable to interact with it, helpless to defend myself… *shudder*
I think I don’t play on these possibilities enough while running a game. For instance, to use the above example, when a character is immobilized by some undead creature, rather than just saying “You’re frozen for the next 6 rounds”, you could get a lot of atmosphere by saying something more evocative like “The ghoul touches you and you feel your muscles freeze, turning to stone. You can still see and hear everything around you, can catch glimpses of your comrades fighting the creatures out of the corner of your eye, but you are just standing there, a completely immobile spectator, waiting for the outcome, unable to affect it.”
So, what really scares you?
Spiders, hands down. SoD poison FTL.
Dead Babies or even undead ones.
Spiders and restriction of movement (i.e., being unable to move when you, theoretically, should be able to).
But Spiders are the big one. They're the reason I don't even remember what the crawl space under my house looks like to this day.
The idea of knowing I'm already dead and there's nothing I can do about it. Especially from some wound that wouldn't dull my senses.
Not being able to perceive reality correctly, and remembering one thing but find out later that you did something very different. See the second "Blair Witch" movie, where the individuals committed murders, etc., but did not realize it do to illusion, thinking they did nothing at all or were acting in self defense, until confronted with the video evidence of what actually happened.
That, and being paralized, of course…