Psychology and Religion: West and East (The Collected Works of C. G. Jung, Volume 11)
If we disregard the specifically Persian system of dualism, it appears that no real devil is to be found anywhere in the early period of man’s spiritual development. In the Old Testament, he is vaguely foreshadowed in the figure of Satan.
But the real devil first appears as the adversary of Christ, and with him we gaze for the first time into the luminous realm of divinity on the one hand and into the abyss of hell on the other.
The devil is autonomous; he cannot be brought under God’s rule, for if he could he would not have the power to be the adversary of Christ, but would only be God’s instrument.
Once the indefinable One unfolds into two, it becomes something definite: the man Jesus, the Son and Logos.
This statement is possible only by virtue of something else that is not Jesus, not Son or Logos.
The act of love embodied in the Son is counterbalanced by Lucifer’s denial ~Carl Jung, CW 11, Para 254