I must admit, I was somewhat surprised to read where “Satan” may not have been an OT concept OR an NT concept for that matter. In a 2016 article “How the serpent became Satan” the author claims, “Introduced as “the most clever of all of the beasts of the field that YHWH God had made,” the serpent in the Garden of Eden is portrayed as just that: a serpent. Satan does not make an appearance in Genesis 2–3, for the simple reason that when the story was written, the concept of the devil had not yet been invented.”
So if Satan was a made up, evolving, figure used in many Bible Stories, who else ? You can read the complete article here.