In Celestial Sin (see the page here for a blurb, excerpt and reviews), the hero is the angel Cam-ael of the Order of the Powers. Here is a little information about that order of angels:
The “Powers” collaborate, in power and authority, with the Principalities (Rulers). The Powers are the Middle Triad shared with the Dominations and the Virtues. The Highest Triad consists of the Seraphim, Cherubim and Thrones. In the Lowest Triad, you find the Principalities, Archangels and Angels.
The Powers are the bearers of conscience. the keepers of history and warrior angels created to be completely loyal to God. It is said that no Power has ever fallen from grace, but another theory states that Satan was the Chief of the Powers before he fell from grace. The duty of these angels is to oversee the distribution of power among humankind. The Chief of their Order is Cam-ael, who bears scrutiny as he exemplifies that wavering path between good and evil. His name means “He who sees God.” Yet in his darker mode he is identified as a Duke of Hell.