I would say though that fear is a hard thing to make a reader feel. Revulsion, hate, loathing, anger, distrust, disgust etc... are much easier emotion to spark off in general.
Yeah, that's the vibe I get. I'm not very experienced with the horror genre, but it seems that the other negative emotions like hate or disgust can many times be carried through with a good depiction of the character/situation alone. With fear, on the other hand, it feels like not only do you have to play with the written event, but with the mood, POV, pace, and the reader (feels like you need to guide the reader very closely in the telling and anticipate physiological reactions themselves) more so than with other emotions, in a very detailed and controlled manner.
The other thing, which goes along with that is propaganda and suggestion.
True. Sauron or Voldemort were scarier when they existed only in hushed superstitious hearsay
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I also think stakes are important - a clear understanding of what is to come.
Yup. What fascinates me is that many non-horror stories coincide with the horror genre's stakes (usually life or death situations). It's interesting to analyze how the context works to twist these similar stakes to induce fear, when these same stakes in another story, do not.
I think too great a disparity in power can reduce the protagonist’s agency, and thus the stakes.
I half-agree. The disparity in power does modify MC agency, but not the stakes IMO. Isn't the horror genre mostly this? MC's terrified reaction after terrified reaction to the baddie's actions, running away, hiding, trying to understand, etc. In the third act proactive behaviour comes into play, but not that much before then. I feel there's an inherent victimization of the characters in order to make the threat as big as possible, thus increasing the stakes.
To give a proper example on the issue, I've been looking back at one of my top 3 horror faves: the original Alien movie. I think it's an horror masterpiece, and although the sequel was more fun for me, it was not as scary. And this comes down to the victims. In the first movie, they had no idea (that's where fear of the unknown comes in) and they were wholly unprepared, with the crew being civilians (that's where the power disparity comes in, compared to an alien). In the second movie the crew members know about the aliens and their rough location (a diminished fear of the unknown) and they are trained soldiers armed to the teeth and with a plan (power disparity practically non-existent, but plenty of character agency--they believe they are in control. In the beginning it even looks like the aliens are the underdogs). The threat level does increase when they loose most of their resources, thus regressing to being powerless in relation to the antagonist. This makes me think that the power relation is more important than the unknown, basically because as a writer you cannot take back exposure and information, but you can take back power given. For the intentions of horror, I feel power ends up being more maneuverable, and thus of greater value (?) to the story.
In my mind, more agency=less perceived power disparity=less fear. And concerning fear of the unknown, now that I think about it: isn't it also an aspect of power disparity? Whoever knows most has the power. If the monster can see you but you can't see it, who has the power? The less information you have, the less power to control the situation you have, thus the less proactivity you can muster. Rather than power, maybe the main factor is the more specific sense of control?
Apologies for the near stream-of-consciousness just now. It's a fascinating subject!