According to the Cambridge International Dictionary of English Mystery is something strange or unknown that has not yet been explained or understood. A mystery is also a book, film or play, especially about a crime or a murder, with a surprise ending which explains all the strange events that have happened. Mysteries are magical and challenging.
Mysteries are magnificent but can be harsh and cruel.
Mysteries are difficult. Horrid stories are dreadful and haunting, but they are interesting. Mysteries are challenging and intriguing and can quickly capture interest. It is the mystery. Writers of horror stories use mystery in their stories to attract the audience.