The fifteenth century philosopher George Gemistos Plethon led a small, secret group worshiping the Greek gods. He hoped to establish a universal Pagan religion based on Ancient Greek Paganism and Neoplatonic theology. His ideas inspired Renaissance mages such as Marsilio Ficino, thus reviving ancient Pagan thought in Western Europe and awakening Hermetic and Neoplatonic spirituality and magic. In this talk I will present an introduction to Plethon's religious rituals and spiritual ideas, as presented in my recent book, "The Secret Texts of Hellenic Polytheism: A Practical Guide to the Restored Pagan Religion of George Gemistos Plethon" (Llewellyn, 2022), which explains and includes the first complete English translations of the parts of his work that survived destruction by his Christian enemies.