It has been my understanding that the concept of the Devil was mostly fleshed out after the Jews camped out in Babylon. When they were later released by the Persians they came in contact with Zoroastrianism and its concept of duality. When the Jews adopted some of this dualism they needed a more developed evil personae to God's good, and so Lucifer was evolved into a more powerful being, who wished to rival God. Is this understanding correct? Some parts of it? None?