Michael Constantine Psellus (1018-1178 C.E) was one of the most notable writers and philosophers of the Byzantine era. The Byzantine domain was effectively the eastern Greek speaking part of the Roman Empire centred on Byzantium (Constantinople, modern Istanbul) which split off from the Latin West in 364 C.E. Its intellectual legacies helped lay the foundations for the Italian Renaissance. It was the fall of Constantinople in 1453 that released a tide of Greek reading scholars into Western Europe, particularly Venice. With them came much of the magical and Hermetic knowledge which the Greeks in their turn had inherited from the Egyptians. The Key of Solomon was one such text. It is therefore essential to the understanding of such magical texts that one understands exactly how the Byzantines understood the nature of daemons. Psellus forms the bridge between the ancient world, Byzantine Greek, and the grimoire conception of the nature of daemons. Hailing from Constantinople, Psellus’ career was an illustrious and practical one, serving as a political advisor to a succession of emperors, playing a decisive role in the transition of power between various monarchs. He became the leading professor at the newly founded University of Constantinople, bearing the honorary title, ‘Consul of the Philosophers’. He was the driving force behind the university curriculum reform designed to emphasise the Greek classics, especially Homeric literature. Psellus is credited with the shift from Aristotelian thought to the Platonist tradition, and was adept in politics, astronomy, medicine, music, theology, jurisprudence, physics, grammar and history.