The Hyperboreans were a race in Greek mythology who lived in a land of sunshine beyond the north wind, worshiping Apollo. Nietzsche referred on several occasions to the free spirits as Hyperboreans
This editorial note to the Red Book establishes the dual valence of the Hyperboreans in Jung’s working context: the classical Apollonian mythologem and Nietzsche’s reappropriation of the figure for the emancipated, beyond-conventional-morality ‘free spirit.’
, The Red Book: Liber Novus, 2009thesis