Can cut a ghost

The scenes grew darker, emphasizing the menacing shapes inside the family’s house at night, until Naomi’s hands shook. Horatio seemed concerned, but Wes—oblivious—whispered about potential ghost weaknesses.
“One spirit can kill another by eating it,” Ryn said, “because they’re made of the same substance. For non-spirits, you must have Hell-fire or something sharp enough to cut a ghost. I only know one such thing.”
“A plus-three vorpal sword?”
An odd piece of lore to know, for a mortal. “Two things,” Ryn allowed. She kept her gaze on the movie screen and the rearview, where Naomi’s eyes were bright with fear. The smell was worse than the parking deck and Ryn clenched her teeth.


Chapter 16, Page 250