Answer:
A plot device that the author used is exposition.
Step-by-step explanation:
Exposition is the author setting the scene by giving descriptive information. In the sentence "The black cat, so mysterious, suspenseful, surprising, or just plain creepy," The descriptive information in this sentence is the adjectives that describe the black cat. For example, the author's word choice of "mysterious, suspenseful, surprising, etc." are all examples of exposition.