The Heart of the Master is a short mystical text written by Aleister Crowley mostly in 1925 while he was in Sidi Bou Said, Tunisia. The work presents a visionary experience in which Crowley proclaims the arrival of the Beast 666 as the Prophet of the New Aeon, governed by Horus, the God of Force and Fire. The text describes spiritual forerunners throughout history who have guided humanity's evolution.