The First of the Fallen, also known as the Dark One, Devil or Satan, is the ruler of Hell and the embodiment of sin and evil.
Banishment from Heaven
As his name suggests, the First of the Fallen was the first angel banished from Heaven and cast down to Hell. Presumably he is also the first angel created by God.
A Blue's musician, by the name of Willie Cole, sold his soul to the First of the Fallen for fame. After a period of time, the First came to claim Willie's soul, while the latter was recording in a studio. The First's voice ended up being recorded on the song Willie was recording at the time. Anyone who picks up the record will become tempted to play it, and if they listen to it, their eyes will start to glow yellow, and the person will falls under a hypnosis and commit suicide.
Powers and abilities
- Angelic physiology: the First of the Fallen is a fallen archangel, thus has immense supernatural powers that are exceeded only by most other archangels and God himself.
- Immortality: Due to him being the First of the Fallen and presumably the first angel created by God, he is beyond age and illness as well as most, if not all forms of physical harm. It can be assumed that the only ones that can kill him are God himself or maybe other archangels.
- Semi-Omnipotence: As the ruler of Hell and presumably the first angel created by God, the First of the Fallen possesses near-omnipotent levels of supernatural powers, that surpasses that of regular angels, and most other archangels; his powers are surpassed only by God himself.
- Necromancy: The First of the Fallen possesses the power to bargain with humans for their souls, in exchange for a wish.
- Dimensional travel: The First of the Fallen is able to travel from Hell to Earth, in order to claim the souls of those who sold theirs to him.
- Mind control: When the voice of the First of the Fallen was recorded on a record, people who listened to it were induced to commit suicide.
- Creation: The First of the Fallen is so powerful that he was able to create millions of demons. 
- "Blast Radius" (mentioned)
DC's Legends of Tomorrow
- "Night of the Hawk" (mentioned)
- Despite a common misconception, the First of the Fallen and Lucifer are two different beings. Although they are very similar in nature and origin, Lucifer Morningstar was the rebel archangel who lead the revolt of the angels, while the First of the Fallen was simply the first fallen angel who was condemned to rule Hell.