The Upanishads answer nothing. It’s just fanciful storytelling.

There is zero evidence that humans each have an invisible ethereal “thing” in our bodies called a “soul” that whooshes out at our death. I suppose this is a fun idea for a fantasy novel, but in terms of the real within in which we all live, the notion of “souls” is make-believe. Ditto Hell. There is zero evidence for its existence.

Who is Satan? I can tell you who Satan is: a fictional character in exactly the same way that Lex Luthor and The Riddler and Mumbles (see Dick Tracy) and Sauron are fictional characters. That was easy.

But, wow, the degree to which religious believers venture deep and far into the rabbit hole of “theology” never ceases to amaze me. Incredible.