Angels are heavenly beings that act to oppose major changes and beings that threaten the universe. If something changes or challenges the universe intentionally and causes a great disturbance, an angel may be dispatched, with the minors ones who have just enough power to handle the situation. They act as a counterbalance for demons, although they cannot win in a one-on-one confrontation with those of the same class (i.e. a lower angel against a lower demon), and those who call upon their powers are Evangelists.
Angels come in different forms, but it is known that the seventh choir exist in abstracts, and it is suggested that there are different choirs, at least seven, that handle different parts of the universe. The lower angels don't have a communication network while the higher ones do.