Q. In my studies, I’ve been troubled by the fact that the Old Testament rarely references Satan. When it does, it is vague at best and usually refers to him in some other form. Also, I understand that there are numerous references to “the satan,” which is actually just a way of identifying an accuser. Some agents of God are even referred to that way in the Hebrew. This all makes me feel like Satan is a creation of the New Testament and that the serpent in the garden, or the antagonist in the book of Job, were just generic characters.
Your question is similar to the one that I answer in this post: How can an evil being like Satan be allowed in God’s holy presence, in the book of Job? In that post, I observe about the character whom the narrator of the book of Job calls “the adversary” or “the accuser”:
“While this character is similar to the devil or Satan described in the New Testament, the portrait isn’t drawn as fully in the book of Job. The book doesn’t account for where he came from or how he became opposed to God. It does portray him as a crafty and malicious player within the complex moral web of the universe, but not necessarily as a consummately evil being who could never be allowed into the presence of a holy God.”
There is actually much debate about whether “the adversary” in the book of Job is indeed an “agent of God,” to use your expression, that is, someone who helps God with the moral government of the universe, something like the “devil’s advocate” (that is, the devil’s lawyer) who, in a saint’s trial, makes sure that all the deeds of the candidate for sainthood are fully considered and assessed, but who is not actually opposed to the candidacy. Many interpreters hold instead that “the adversary” is trying to harm Job because he genuinely believes that Job lives in a righteous way simply to receive blessings from God—this character is not capable of believing that people would obey God out of pure devotion. Personally I see the character more in that way, as sinister and malevolent, not working for God’s best interests.
So already in the book of Job, the portrait of Satan is being fleshed out. But I think this is actually one of those teachings that develops over the course of the whole Bible and finds its fullest expression in the New Testament. I think this is the nature of God’s revelation in the Bible: It is progressive; we have to follow the trajectory of a doctrine through all the pages of Scripture to appreciate it fully. I don’t think we can expect every doctrine to be fully articulated on every page right from the start.
Indeed, the New Testament itself indicates how its understanding of Satan expresses a doctrine that has developed throughout Scripture. In the book of Revelation, Satan is symbolized by a dragon, and Revelation explains that the dragon is “that ancient serpent, who is called the devil and Satan.” So Satan is not a creation of the New Testament, but the fullest understanding of this figure who is diametrically opposed to God is found in the New Testament, which nevertheless helps us trace its own understanding back through the pages of Scripture.