The Order of the Blackened Denarius, usually just shortened to Denarians, is an organization of fallen angels who are bonded with human hosts. There are thirty of them, fourteen of which are currently in possession of the church as far as we are aware
Whoever has a coin can draw on the Fallen’s power: use it to shapeshift, heal wounds and more. Many have been alive for a long time, and some have developed talent for magic. Harry calls them certifiable nightmares. They are very hard to kill.
Their ability shift into a form more suitable for fighting usually arms them with such weaponry as claws, fangs, horns, poisonous bite, hair that is razor-blade sharp, that sort of thing. Molly calls that ability “Battleshifting”. Each Fallen has their own preferences that seem to adapt to the holder of the coin.
They have a cult of human goons with their toungues cut out. And, they have guard dog-like creatures that are ugly, fast and have big teeth. What makes them the most dangerous is the Fallen, themselves. They are older than time and have spent thousands of years learning the mortal world and the mortal mind. They understand things humans can’t grasp. They know every trick and move. They are riding shotgun with each holder or in the driver’s seat. They have a perfect memory and a vast library of information.