Final answer:
The figurative language device used in the sentence is personification, where breezes are given human-like abilities to whisper and interrupt a dream.
Step-by-step explanation:
The figurative language device used in the bold sentence "Before daybreak the breezes whisper through the trellis at my window; they interrupt and carry off my dream, and he of whom I dreamed vanishes from me." is known as personification. Personification is a literary device where human qualities are given to animals, objects, or ideas. In this particular sentence, the breezes are personified as if they have the ability to whisper and to interact with the dreamer's dream, causing the dreamt person to vanish.