Generate an opening sentence for a horror story that occurs in an abandoned castle.
As the full moon illuminated the desolate walls of the abandoned castle, an eerie chill ran down my spine, and I couldn't shake the feeling that I was being watched.
Complete the following task based on the instruction and optional input provided.### Instruction:
Generate an opening sentence for a horror story that occurs in an abandoned castle.

### Output:
As the full moon illuminated the desolate walls of the abandoned castle, an eerie chill ran down my spine, and I couldn't shake the feeling that I was being watched.