Note that, regardless of whatever the earliest function of (a) 'satan' was, even in the Hebrew Bible this was conceived of as a being that could simply take up "certain less pleasant aspects of the deity’s work" (to quote Strokes 2009, writing about the ambiguity of the term in the Hebrew Bible). But not only did this satan take up the unpleasant work of the deity, but could also be the one “responsible” for leading someone to commit a sin or make a bad decision (cf. this; and in the New Testament, see Luke 22:3 and Acts 5:3). In fact, there's a post still at the top of AskHistorians that's a good example of this, about the so-called “Satanic verses” of the Qur'an. In this case, there were some verses originally present in the Qur'anic text that early Muslims considered highly embarrassing – and so later apologists ascribed their original composition to “Satanic” influence.

These functions transfer over quite easily to several different ideas. For one, this need not be limited solely to individuals. One could imagine groups of people being collectively misled by this evil force. Second, a range of negative things could be ascribed to this evil being: which is where we can see a tie-in with demonic possession and such (Mk 2:23, "How can Satan cast out Satan?").

What motivated these innovations is a complicated question. In early Judaism and Christianity, we could perhaps imagine that Iranian (cf. Zoroastrian) ideas had some influence on the idea that a large portion of humanity can be “enslaved” to forces of darkness. Qumran (the DSS) is a good place to look for stuff relevant to this. There could also be tie-ins with Greco-Roman astrology, or the idea that people (or even entire nations!) could have their own supernatural “guardian” (which, in the case of the “enemy” – like Rome – would be thought of as a malevolent being). You might also want to look into Mastema from the book of Jubilees.

I gotta run for a second, but I'd be happy to expand on any of this soon. As for some of the more specific things you mentioned: the Book of Enoch certainly had an enormous influence on more general demonological ideas in the mid/late Second Temple period. The only mention of Satan (Sataniel, IIRC?) comes from the Parables/Similitudes, which was the latest written section. This is the earliest instance in which the serpent in the garden is explicitly associated with Satan.

As for the Greek Life of Adam and Eve: these days, this is usually held to have been composed quite a bit later than the writings of the New Testament. So it's probably not of great relevance here (though some of the ideas that appear in it certainly have a longer history).

It was under my impression that when Jews were exiled from the Holy Land and sent across the Middle East into a diaspora, Zoroastrian influences entered the religion and the idea of Good versus Evil came into being, but that happened far before Christianity, so I'm curious as to whether it was because of that or not.

So to add to the original question, did Zoroastrianism influence Judaism and add the conflict of good versus evil or did it influence early Christianity and add the conflict of good versus evil? I'm expecting that whoever can answer OP can also answer this question too.

It's important to remember that there really is not a consensus on the origins of satan within the christian church. Some denominations do not even recognize the devil as a real entity. Others, especially presbyterian reformed members, believe that satan is very real and is very active in todays world.

According to reformed theology satan held, as you had mentioned, a high position in heaven. This concept as well as the reason and subsequent fall, can be seen in Isaiah 14:9-20. Though the hebrew scriptures mention satan only 14 times in the entire old testament, only three of those occurrences fall outside of the book of Job. Most reformed people will sight those verses in Isaiah as one one those instances.

Contemporary understanding of satan is that he is the author of evil and temptation. However, in ancient hebrew days, the jews understood god to be the sole mover and shaker of all things. Including evil and temptation. God gave you fortune and he took it away.

The concept of satan really started in Babylonia while the jews were in captivity. Persian religion was strong in duality deities and the concept of a dark lord dishing up famine, illness and general shit was strong. The Israelites were quick to adopt this given there current misfortunes. The book of job was likely written during this time.

A full description of who and what satan is wasnt really presented until the new testament. There he is a very prominent figure. He tempts christ, he unleashes demons and is credited as the cause of judas betraying jesus. Notice that in all new testament scripture that no one had issues with satan being in the mix of all this. This tells us that satan, as the evil doer, is very present and highly accepted with in the jewish culture by this time. The new testament is said to have been started about 400 years after the last book of the old testament was written.

The book of revelation makes several references to satan. Even calling him the "snake". This is where people start to put two and two together. This is the same snake that was in the garden of eden in the book of genesis. This is the guy that tricked eve into eating the apple and in doing so introduced sin into the world.

Then you bring in the doctrine of original sin. This is where the dispute really starts. Not to go into it much here but most take one of two sides, original sin (total depravity) is scriptural proof that all need christ as savior since we are all born in sin. Or their was no original sin (not born into sin) and there fore christ is a gift of redemption for all despite everything. Thats a severe over simplification, but you get the gist.

If you buy into total depravity then you sight gen 3:15 as the covenant of grace, the first promise from god and the first hint at christ coming to earth. You need this because your sinful blah blah blah....

That all being said, I am not a historian, I have just had the displeasure of being around some fundamentalist reformed/puritan christians quite a bit and so this is mostly a regurgitation of things I have picked up.

I'm a Jehovah's Witness who has done extensive research on this and other subjects. Allow me to shed some light on the information I have found on the character known as 'Satan':

First off, I will quote a few scriptures to show what information the Bible itself gives on this figure. I know this subreddit is about historical documentation but as this is a somewhat religious question hopefully this will be okay.

In many places in the Hebrew Scriptures, the word sa·tan′ appears without the definite article. Used in this way, it applies in its first appearance to the angel that stood in the road to resist Balaam as he set out with the objective of cursing the Israelites. (Nu 22:22, 32)

In other instances it refers to individuals as resisters of other men. (1Sa 29:4; 2Sa 19:21, 22; 1Ki 5:4; 11:14, 23, 25)

But it is used with the definite article ha to refer to Satan the Devil, the chief Adversary of God. (Job 1:6, 2:1-7; Zec 3:1, 2)

The verses in Job and Zechariah are perhaps the oldest recordings of Satan used as a definite article. These passages refer to Satan acting out against God's interests by attacking one of his servants in Job and Satan being rebuked by an Angel of God in Zechariah.

The name 'Satan' isn't exactly a name either, and whatever his real name is we don't know it. As I said earlier, 'Satan' by itself is defines as a sort of 'resistor' or 'rebel'.

The examples in Job and Zechariah show that even in the Old Testament Satan was not an 'idea' or a symbol of evil, but was an actual person.

As far as modern beliefs regarding hellfire and eternal torment these are teachings that were adopted from non-christian origins.

The Grolier Universal Encyclopedia (1971, Vol. 9, p. 205) under “Hell” says: “Hindus and Buddhists regard hell as a place of spiritual cleansing and final restoration. Islamic tradition considers it as a place of everlasting punishment.”

If you check out http://en.wikipedia.org/wiki/Hell you can see that numerous religious bodies had their own concept of hell. The Bible itself does not include a 'Hell' but certain churches added and encouraged this concept. It is not a coincidence that the Norse underworld as well as its ruler were named 'Hel'.

-Cleasby-Vigfusson, pg. 255, s.v. "hel-viti"; pg. 718, s.v. "viti"

-Hensleigh, pg. 233, s.v. "Hell"

As far as the other modern interpretations of Satan in regard to his position as an evil ruler of the world, 1 John 5:19 says: "We know that we originate with God, but the whole world is lying in the power of the wicked one." This verse along with the previous ones I quoted could easily lead Christians to believe that Satan is the evil ruler of the world.

Anyone have suggestions for academic texts, articles, etc. addressing this question?