Demons In Horror And Humor is relevant to Poul Anderson Appreciation and to James Blish Appreciation but was posted on Personal and Literary Reflections as part of the current reading of Alan Moore's Jerusalem.
How often does Poul Anderson's fantasy feature demons in the Biblical sense? Not often. Pagan gods predominate. How often does Anderson treat demons seriously? Perhaps even less often? The "Devil" in The Devil's Game is most parsimoniously accounted for as a delusion afflicting just one human character.
Of course, Anderson wrote many uncollected short stories. Fresh information about any such works is always welcome.