I'm not going to get involved in the doctrinal squabbles between sects. If they consider themselves Jewish - as they did, and the peers around them consider them Jewish - as they did, I'll just take their word for it.

The texts I'm talking about starts with Enoch in the 3rd or 2nd century BCE. and followed by texts such as Baruch, Apocalypse of Zephaniah, Apocalypse of Elijah, Apocalypse of Peter, Apocalyse of John, etc. And you find "tours of hell" in the Palestinian Talmud and Midrashes like the the Hebrew apocalypse of Moses (Gedulat Moshe). The texts might not refer to Satan by name, but the character we have grown to love is certainly there all along from Enoch all the way to Medieval texts and beyond.

The interesting thing is this tradition spans a good 1000 years and you can totally see the transition from Judaism to Christianity. First the fully Jewish texts, then Jewish texts that have been Christianized and finally completely Christian texts (why I included Christian text above").

Fascinating stuff.