A fallen angel is a wicked or rebellious angel that has been cast out of Heaven. The term "fallen angel" does not appear in the Bible, but it is used to refer to angels who have sinned, those who were cast down to the Earth in the War in Heaven, Satan (Lucifer), or other demons.
In Christianity, Satan is often seen as the leader of the fallen angels. The Book of Revelation tells of "that ancient serpent, who is called the Devil and Satan, the deceiver of the whole world", being thrown down to the Earth together with his angels.
The Fallen Angel is one of the five lady bats encountered in Castlevania: Circle of the Moon. She is found in an exterior area of the Chapel Tower, among the farthest towers that conform Camilla's Castle, and guards the entrance to the Battle Arena.
Similar to other lady bats of her kind, the Fallen Angel soars through the sky with great agility and bears a circle of five energy rings around to protect her. After making a few swoops, she will send forth these rings toward Nathan, which will track him down for a while and then return to her.