What I really think is that Satan is a chatolic invention. The word is derived from arabic, considered a filthy tounge in the middle ages, and means adversary.
Since we're talking fable here, I'll tell a story.
God didn't want to interfere in creation even though he saw that humans stumbled in the dark. The devil pitied the humans and pleaded their case before god. He begged god to let the humans into heaven when they died, but god said no. Those who are ready will find their way, he said.
(God created everything as an experiment to answer the questions of his own origin and identity. To see if it might produce beings like himself. He doesn't want to interfere)
Anyway, the devil pleaded with god, and god asked him if he was challenging his divine plan. Then the devil asked god to live one lifetime as a man, to witness their existence, then he would see that they should be let into heaven. God does this, and we all know how that went.
But before he does this he grants the devils wish. He casts him out of heaven and says that he cannot come back to live in heaven until all the souls of humans have come. He has to be the last. That is the punishment he gets for not trusting in god totally. He becomes the adversary. But over what? The devil was our advocate.
Here's Tom with the weather.