Q: Contrary to what people may assume, Satan is barely a presence in the Old Testament. What is he like?
A: There about five Old Testament stories in which Satan is kind of an incidental character. In the Book of Zechariah, he's the devil's advocate, so to speak, for the Lord. In Book of Numbers, he's not even a person. He's an angel.
The Jewish view is that Satan is always under the command of the Lord. Satan is one of his servants, one of his army.
Q: So the Satan of the Old Testament is basically a lackey, a kind of minion?
A: He is. In the book of Job, he can't do anything that the Lord doesn't authorize. He says, 'Let me do this thing,' and the Lord has to say, 'I'll give you this much permission. You can go this far.' He can't go any further.
Satan is not a rival to God at all. He's a servant.
Q: Did the early Jews ever view Satan as evil?
A: The only place I could find that is when Jewish groups split. It's only when God's people are divided that you get an angel who turns against the Lord.
It's a way of defining your enemy as the enemy within. Members of one sect see all the Jews who don't join the sect as the sons of darkness: We are the sons of light and other Jews are the sons of darkness.
Q: The New Testament offers much more visceral descriptions of Satan and demons. What changes?
A: If you look at the Gospel of Mark, it's full of demons. In the Gospel of John, Jesus is God incarnate and Satan incarnate is the son of darkness.
And Satan, of course, is in the Book of Revelation.
http://www.csmonitor.com/Books/chapter-and-verse/2014/0613/The-Origin-of-Satan-author-Elaine-Pagels-discusses-the-religious-figure-s-modern-conceptionCompare Bede
Another of the king's chief men, approving of his wise words and exhortations, added thereafter:"The present life of man upon earth, O king, seems to me, in comparison with that time which is unknown to us, like to the swift flight of a sparrow through the house wherein you sit at supper in winter, with your ealdormen and thegns, while the fire blazes in the midst, and the hall is warmed, but the wintry storms of rain or snow are raging abroad. The sparrow, flying in at one door and immediately out at another, whilst he is within, is safe from the wintry tempest; but after a short space of fair weather, he immediately vanishes out of your sight, passing from winter into winter again. So this life of man appears for a little while, but of what is to follow or what went before we know nothing at all. If, therefore, this new doctrine tells us something more certain, it seems justly to deserve to be followed."
http://www.sacred-texts.com/chr/bede/hist049.htm