The concept of an ascending hierarchy of different orders (or
choirs) of angels is common to all traditions of
angelology. There is a variety of versions regarding the names
and the number of choirs. The best known Christian version was
devised in the sixth century by Dionsyius the Pseudo-Areopagite, a
Syrian monk, who elaborated this system in his work, The Celestial
Hierarchies. This became established in mainstream Western culture
as the classic work on the subject, and was adopted in the epic angel
sagas of Dante and Milton. This system consists of nine choirs
grouped in three triads.
