I attempt to read the Bible counterculturally. I was raised in a hitech civilization with strong secular and Christian crosscurrents. That's completely different from the world of the Pentateuch, where paganism and witchcraft were pervasive. So I like to ask myself how certain Biblical narratives might come across to people with a background that's more like ancient pagans.
I haven't done in-depth study of fox spirits, but from what I've read, it's a fixture of Chinese and Japanese folklore. Here's one example:
There are different ways to interpret this kind of material:
i) We might discount it in toto as sheer folk mythology.
ii) By the same token, we might discount it on the grounds that where there's a preexisting explanatory category, many people default to that generic category.
iii) Or we might say it has a basis in fact, but it's undergone legendary embellishment. In other words, this derives from actual encounters with malevolent supernatural agents, but as a result, people invent a backstory to explain where these "spirits" came from, where they normally reside, how their world intersects with our world. Stories about their origins, social order, &c., are mythological, but a genuine experience underlies the narrative overlay.
I'm sure that (ii) is often the case, but I also think (iii) is likely to be the ultimate reason.
If fox spirits exist, what are they? In principle there are three possible candidates:
i) Animal spirits
ii) Demonic spirits
What's notable is the distinction between a physical animal and a roaming "spirit" that's detachable from the body. Given the association in some cultures between animals and malevolent free-ranging "spirits," it may be instructive to consider how the Tempter in Gen 3 would register to the original audience. What cultural connotations would that evoke?