Foreshadowing or adumbrating is a literary device in which an author indistinctly suggests certain plot developments that might come later in the story.
Flashback– A shift in a narrative to an earlier event that interrupts the normal chronological development of a story. Contrast with flashforward.
Irony– Henry Watson Fowler, in The King’s English, says “any definition of irony—though hundreds might be given, and very few of them would be accepted—must include this, that the surface meaning and the underlying meaning of what is said are not the same.”
Also, Eric Partridge, in Usage and Abusage, writes that “Irony consists in stating the contrary of what is meant.” We can therefore apply a generic understanding that irony is when something unexpected occurs in a story.
Verbal irony occurs when a character says something that is interpreted differently that what he/she intends.
Dramatic irony occurs when the reader/audience is aware of something that the character is unaware of.
Situational irony occurs when actions taken have an effect exactly opposite from what was intended.
Symbolism is when an object, location, season, animal, plant, etc is used to represent a deeper understanding of some other unassociated development.