Fear. The word just sends shivers down your spine by simply hearing it, right? This is my absolute favorite thing to write about; manly because you can do anything and everything with it. Fear can create, sadness, loneliness, anger, resentment, insanity; it's like a god of emotion itself. Writer must control the fear in their characters and stories, because fear is the wildest thing there is. Making a character scared can cause numbness and shyness in their persona. It can be the greatest power anybody can have and control. That is us, that one person; the creator, the writer, and the builder of the fear that our characters have.
To create fear, there must be a root source; and many fears can branch out from it. Falling into a pit of lava and falling into water might be caused by a fear of falling in general. Although, there are many of the basic fears that a lot of people have: The dark, spiders, heights, shame, embarrassment, clowns, and donkeys (Well... Maybe the donkey thing is just me). Anyway, there are also fears that come for no reason: Heights, the dark, people ect. Then there are fears that come from different things. THIS is what you must play with.
Having this can make your book amazing and slightly frightening itself (which is what you want). It brings the reader in and wants them to read more about it. Make sure to never give away the fear all at the beginning or all at once; that brings on a terrible plot.
this is where i ramble; have fun