Singular: Seraph. In the pseudo-Dionysian celestial hierarchy, the Seraphim are the highest level of angels. “[They] surround the throne of God and unceasingly intone the trisagion (‘holy, holy, holy’). [According to] Enoch 3, there are 4 [seraphim]. The ruling prince…has been given variously as Seraphiel, Jehoel, Metatron, Michael and originally Satan before he fell. Some of the order defected at the time of the great rebellion.” (Davidson.)
