Atmosphere

In gothic writing, I believe atmosphere is the most integral part of the story's emotional effect. The story Frankenstein could have easily had Victor animate the monster and that was it. It would have been a bit creepy, but not amazingly scary. It's when Shelley adds the dark, stormy night, and describing how the lab was dark that makes the situation all the more scary. If you have a story where there is no atmosphere, and it pretty muck takes place in a room with nothing in it, people will not read with anxiety of what will happen. Atmosphere is what makes a story have the underlying horror of a story.