Sefer ha Sitra Achra

The metaphysical system of the Holy Kabbalah posits a vertical and positively-aligned Tree of Life, through which energy from the earthly plane flows upward in a series of experiences culminating in union with the Divine Source. However, in some forms of Jewish Mysticism, there exists an averse, or Dark Side of the Tree, whereby energy is used to direct personal will, and change reality for good or evil. The Sitra-Achra explicates these ideas, steeped in ancient tradition, yet providing the magical practitioner with tools to navigate both light and dark forms of the Tree of Life. (Publisher)