This harkens to religion and explaining the problem of evil.
The biblical narrative has Eve tempted by one called the Tempter, who, in history, is called Satan, the Adversary, the Dark Angel, Lucifer, etc.
One of the deepest questions believers hvae about religion and a God who creates all, and "saw that it was good" the problem of evil is the question of whether evil exists and, if so, why. Evil is the absence of Good. Why does God allow evil? It is argued that evil is not created by God, but that God created mankind who has the choice to commit evil acts.
A possible answer is that the world is corrupted due to the sin of mankind. Some answer that because of sin, the world has fallen from the grace of God, and is not perfect. Therefore, evils and imperfections persist because the world is fallen.
Biblical narrative posits the existence of a Fallen Angel, the Adversary, who is mankind's tempter. This Fallen Angel or Adversary is variously called Satan, Lucifer, or The Devil. The same exists in the Koran, where the Lucifer or the Adversary is called Shaitan, a dark angel who is constantly tempting every man, woman and child all day long, everyday.
Augustine of Hippo wrote that the genesis story that essentially dictates that God created the world and that it was good; evil is merely a consequence of the fall of man (The story of the garden of Eden where Adam disobeyed God and caused inherent sin for man). Augustine said that natural evil (evil present in the natural world such as natural disasters etc) was a direct result of the fall of man, whereas moral evil (evil caused by the will of human beings) is as a result of man having become estranged from God and choosing to deviate from his chosen path.
So having a Lucifer explains a lot of things in Christian Dogma.
- that man does evil
- that the flesh is mortal
- that Jesus took flesh, was born and died to redeem man from sin