The Celestial Hierarchy De Coelesti Hierarchia ( Celestial Hierarchy ) is a Pseudo-Dionysian work on angelology (dated to ca. the 5th century) which exerted great influence on scholasticism.
An angel is a supernatural being or spirit, usually humanoid in form, found in various religions and mythologies. The theological study of angels is known as "angelology". In Zoroastrianism and Abrahamic religions they are often depicted as benevolent celestial beings who act as intermediaries between Heaven and Earth, or as guardian spirits or a guiding influence.