"Then the Lord God said, "Behold, the man has become like one of Us, to know good and evil. And now, lest he put out his hand and take also of the tree of life, and eat, and live forever"—therefore the Lord God sent him out of the garden of Eden to till the ground from which he was taken. So He drove out the man, and He placed cherubim at the east of the garden of Eden, and a flaming sword which turned every way, to guard the way to the tree of life."
Genesis 3:22-24
Adam and Eve were cast out of the Garden of Eden, cursed to bear children, and live mortal lives.
"Now Adam knew Eve his wife, and she conceived... and said, "I have acquired a man from the Lord."
Genesis 4:1
And that man was the firstborn man, Cain. Then came the second born.
"Then she bore again, this time his brother Abel..."
Genesis 4:2
The brothers both worked with different things.
"...Abel was a keeper of sheep, but Cain was a tiller of the ground."
Genesis 4:2
This caused quite a dispute.
"And in the process of time, it came to pass that Cain brought an offering of the fruit of the ground to the Lord. Abel also brought of the firstborn of his flock and of their fat. And the Lord respected Abel and his offering, but He did not respect Cain and his offering."
Genesis 4:3-5
This is made Cain very angry. This anger made Cain do something bad.
"Now Cain talked with Abel his brother; and it came to pass, when they were in the field, that Cain rose up against Abel his brother and killed him."
Genesis 4:8
In doing this, it caused God to bestow a curse on Cain.
"So now you are cursed from the earth, which has opened its mouth to receive your brother's blood from your hand."
Genesis 4:11
With this, he, Cain, was cursed to be a fugitive and Vagabond of the earth.
With Cain cursed to live an immortal life, with the guilt of killing his brother, he sought revenge against God. He thought God was evil, so he made a deal with the Devil. The Punisher of Evil. Lucifer Morningstar.
And that is where the story began.