The most influential Christian angelic hierarchy was that put forward by Pseudo-Dionysius the Areopagite (4th or 5th century) in his book De Coelesti Hierarchia (On the Celestial Hierarchy). He created a schema of three hierarchies (spheres or triads of angels), with each hierarchy containing three orders or choirs. Angels of the first sphere serve as the heavenly counselors. A seraph is an angelic being, regarded in traditional Christian angelology as belonging to the highest order of the ninefold celestial hierarchy, associated with light, ardor, and purity. Tradition places seraphs in the fifth rank of ten in the Jewish angelic hierarchy. Taken from "The Hierarchy of the Blessed Angels. Their names, orders and offices the fall of Lucifer with his angels" by Thomas Heywood. Copper-plate engravings by Adam Islip, 1635.