THE RAVEN 

In order to keep the reader on the edge of his or her seat you need a victim (a protagonist who finds himself/herself in a situation of uncertainty, helplessness and is paralyzed by fear). Fear is the driving force of any horror story.

The cause of the fear may include spirits, goblins, ghosts, paranormal phenomena, werewolves, vampires, witches, creatures from beyond the grave, haunted houses ...

To create the right atmosphere you must think about using the foreshadowing technique, which implies preparing the reader for the impact of the climax by slipping apparently minor details here and there.

Suspense is what keeps the reader interested in the story. It consists in maintaining the fear with expectation of what will happen next.

Mystery implies that something surprising will happen. This "something" can be rational or irrational, that is, inexplicable (after all, that is the essence of mystery).

Last, but not least, imagination. You must use your imagination, which combined with the other elements, will help you write a good and memorable terror story.