Isaiah 14:12-14 is where the Devil shows up under the name "Lucifer" (or "Day Star") for the first time—though, actually, this passage probably doesn't refer to the Devil. It seems to be referring to the King of Babylon, prophesying his downfall. Like the planet Venus, the Morning Star, he fades out as the morning of God's Judgment dawns:
How you are fallen from heaven, O Day Star, son of Dawn! How you are cut down to the ground, you who laid the nations low! You said in your heart "I will ascend to heaven, I will raise my throne above the stars of God."
So, even though this is apparently meant to attack a King of Babylon, it actually does allude to an older Canaanite myth about a god who revolted against Ba'al (the king of the gods) and was forced to retreat into the underworld. Throughout history, it's inspired a great number of the stories surrounding Satan, particularly the tale of how he revolted against God and attempted to establish his own kingdom—most famously retold in John Milton's Paradise Lost.