What is the proper use of dashes within a sentence to set apart something surprising?

Use dashes to set off appositives that contain commas; in other words, if you are renaming a nearby noun with something that contains commas, use dashes to set if off.  

OR.

Use a dash to prepare for a list, a restatement, an amplification, or a dramatic shift in tone or thought.

a simile is first defined as a type of speech that uses one thing or phrase with comparisons to things of an unrelated kind, often in order to make a more vivacious description. so of the phrases above, only the last one (i swear she cast a shadow white as stone) would be considered a simile, as a shadow white as stone takes two unrelated things and uses them in an interesting way.

explanation:

mark brainliest and have a great day!