In the moment fear existed, love could exist as a thing that could be experienced.
It is this creation of duality between love and its opposite which humans refer to in their various mythologies as the birth of evil, the fall of Adam, the rebellion of Satan, and so forth.
Just as you have chosen to personify pure love as the character you call God, so have you chosen to personify abject fear as the character you call the devil.
Some on Earth have established rather elaborate mythologies around this event, complete with scenarios of battles and war, angelic soldiers and devilish warriors, the forces of good and evil, of light and dark.
This mythology has been mankind's early attempt to understand, and tell others in a way they could understand, a cosmic occurrence of which the human soul is deeply aware, but of which the mind can barely conceive.
In rendering the universe as a divided version of Itself, God produced, from pure energy, all that now exists—both seen and unseen.
In other words, not only was the physical universe thus created, but the metaphysical universe as well. The part of God which forms the second half of the Am/Not Am equation also exploded into an infinite number of units smaller than the whole. These energy units you would call spirits.
In some of your religious mythologies it is stated that “God the Father” had many spirit children. This parallel to the human experiences of life multiplying Itself seems to be the only way the masses could be made to hold in reality the idea of the sudden appearance—the sudden existence—of countless spirits in the “Kingdom of Heaven.”
In this instance, your mythical tales and stories are not so far from ultimate reality—for the endless spirits comprising the totality of Me are, in a cosmic sense, My offspring.
My divine purpose in dividing Me was to create sufficient parts of Me so that I could know Myself experientially.