Heinrich Cornelius Agrippa von Nettesheim was a medieval scholar who was influenced by Platonism, Neoplatonism, and Hermeticism. His most famous work,
De occulta philosophia libri tres (1531), explores magic, astrology, alchemy, theurgy, medicine, mysticism, and more, and this book was a major factor in the spread of the occult sciences. Agrippa’s theology, though nominally Roman Catholic, was generally disliked by the Catholic church as it attacked the church’s abuses. At least once he was jailed and branded a heretic.
Giordano Bruno made use of his writings, and their influence was long and powerful.