Lucifer means literally 'Light Bringer.' In Christian tradition this is another name for Satan or the devil. In the Biblical story, Lucifer sinned by pride, wishing to outshine God himself and thus was cast out of heaven.
In the Cassiopaea material, the legend of Lucifer is likened to the history of humanity. Humanity is collectively the fallen angel, as well as the prodigal son of the New Testament parable. The Old Testament's account of God and Devil or Lucifer is seen more as a game of good cop vs. bad cop, where the same Yahweh or Demiurge plays both sides. Indeed, both are about equally bloodthirsty.
In the account of the Fall, as rendered in the Cassiopaea material, humanity was indeed tricked and fell, whereas the forces inducing this fall were quite consciously of the STS polarity and not fallen in the same sense.