In many American sci-fi/fantasy fictional works, there's a trope about Nazis creating/attempting to create/use supernatural weapons/monsters (examples Hellboy movie, Indian Jones movie etc.) What, if any, is the historical basis of this trope?
This merges two historical facts:
Nazis general attempt to use cutting edge science (Both USSR's and USA's space programs are basically bastard children of Nazi rocket research; they had jet fighters before any other power, etc...)
Certain strata of Nazi society being extremely interested in and involved with occult. Part of that was general "Aryan race is descended from advanced precursor civilization" meme (with the precursors being from a merge of Hyperboria and Atlantis legends) - see Thule society. Part of it was a lot more spiritual/occult, though most information out there on the topic is conspiracy theoryish with no documented proof.
The Nazis had some bizarre supernatural beliefs and Himmler himself created a branch of the SS concerned with investigation of the supernatural called the Ahenenerbe. They sent investigators to Tibet to learn eastern mysticism.
The Nazis believed in some kind of supernatural beings called the Vrill people who were supposed to reside within the earth. I don't know an awful lot about this but it is something one could research.
The most disturbing aspect was experiments on human subjects at Dachau which gave rise to the myth of Nazi Zombies. This was experiments where camp inmates were literally frozen to death in cold water and then efforts were made to re-animate their corpses.