To what extend do I think Shelley achieved this original goal?
I busied myself to think of a story… One which would speak to the Mysterious fears of our nature and awaken thrilling horror
I think Shelley has achieved this original goal quite well. She has chosen many ideas about the mysterious fears of our nature. For example, Victor Frankenstein is meddling with things that are beyond our or his knowledge. She has done exactly what she had intended which was to create a thrilling horror about the mysterious fears of our nature. The creature Victor makes is the fear of our nature. That is what happens when you mess with nature.