Foreshadowing

Definition
A literary device that authors use to hint at what is coming later in the story.

Examples
Romeo and Juliet Act 2, scene 2.

"Life was better ended by their hate,

Than death prorogued, wanting of thy love."

Lord of the Flies, Page 84-85

"Last night I had a dream, a horrid dream, fighting with things. I was outside the shelter by myself, fighting with things, those twisty thing in the trees. And I was frightened and started to call otu for Ralph and then I saw something moving among the trees, something big and horrid."