The Church of Satan
I've looked at some stuff recently on Satanism (just out of curiosity - I'm not a Satanist). They don't believe in a being called Satan, but they do believe that there's a dark side of nature that maybe comes through in stories of Satan and demons. They also don't sacrifice children or animals.
Reading about Satanism made me wonder what kind of religion our descendants might end up with. In a declining civilization when it seems like the world is upside down, maybe religious ideas and symbols get turned upside down too. In the future, could Satan be seen as good? Could the Sigil of Baphomet replace the Cross?
I once read an article that claimed that before Judaism, Satan wasn't The Bad Guy. The author, whose name I totally forget, said that the Jew's ancestors worshiped the devil before they gave him an evil makeover. I don't know if that's true, but it was a fascinating article.