Thinking about trolls (+elves, huldufólk, others) in light of Eduardo Vivieros de Castro. I'm not willing to say that pre-Christian Scaninavians were perspectivists in Amazonian style, but I do think that looking at Norse religion and later Nordic folklore through that lens is productive.
I'm mostly using the word troll as kind of a catch-all (which is not unlike how Scandinavian folklore uses it, though Icelandic folklore does not).
There are two main fears concerning trolls: that they will eat you, and that they will marry and/or fuck you. In Levi-Strauss's time that might have been seen as symbolically reducible to the same fear, but I think we can learn more by examining them in their distinction.
I dunno that I can summarize Vivieros de Castro's points here, but I'm reading from Cosmological Perspectivism in Amazonia and Elsewhere: Four Lectures given in the Department of Social Anthropology, Cambridge University, February-March 1998.
In western ontology we humans are like animals in that we have bodies, but what distinguishes us is the soul (or the rational mind, or whatever, the details change over time but the point is something distinctive about our interiority), so that for, say, Christian missionaries, "because the spiritual is the locus of difference that
conversion becomes necessary (the Europeans wanted to know
whether Indians had souls in order to modify them)." Sverrir Jakobsson says that Icelanders bought so heavily into the [Christian : Heathen] distinction as the primary ordering principle of the peoples of the world that they had trouble recognizing, or even outright denied, that there was an East-West split in Christianity.
In perspectivist ontologies this is flipped, the locus of differentiation is the body, because the interiority of everything is the same, difference comes from inhabiting different bodies. If you could acquire the sight of a jaguar, you would look at a puddle of blood and see a nice cold beer (but you would also be dangerous to humans, because you would see them as game animals). The resulting anxiety is cannibalism. If everything is the same in underlying essence, it becomes necessary to engage in an active practice of differentiation to avoid eating something that is the same as you. Ritual specialists who can transform into animals are sometimes bad hunters because they are too deeply engaged in this paradox.
The fear of marrying a troll (or elf, whatever) is the fear of spiritual conversion. This is sometimes made explicit: "I don't want to live with elves; rather, I want to believe in my Christ" -- Ólafur Liljurós (note that while this ballad is related to similar ones all over Europe, many of them deal with the protaganist's impending marriage and/or infidelity in some way; this is absent from the Icelandic and it's a purely religious conflict). In Tungustapi, Sveinn doesn't just fuck elves, he also goes to their church (which is a sort of inverted Christian church). He's alienated from the [Christian/human] community. This corresponds to "western ontology."
The other side of this is fear of being eaten. At risk of overthinking things, because being afraid of a scary monster eating you doesn't really seem to need a lot of explanation, I think there are religious/cosmological implications here.
The fear of being eaten by a troll is different from the fear of being eaten by a bear or a boar, because humans also eat bears and boars, we are on the same level with them. You can't eat a troll (we also don't eat wolves, and wolves are trolls' domestic animals, although I guess you could eat a wolf). A semi-human semi-Euhemerized jötunn/troll is associated with cannibalism in Orms þáttr Stórólfssonar. I've written before about the likely etymological derivation of jötunn from a word meaning 'to eat'; previously I said that while *etaną 'to eat' and *etunaz 'jötunn' have a clear etymological relationship, that might not be so a few hundred years later when they have become eta and jǫtunn, but maybe this relationship should be reconsidered.
Eduardo Kohn was once told to always sleep on his back in the jungle, because if a jaguar comes it will see his face and recognize him as a person, but if it sees his back it will see him as prey. To avoid being eaten by a troll you have to get the troll to see you as a person and not as food, you can do this by giving a gift (and initiating a relationship of reciprocity), or else by being more troll-like yourself (maybe even by preestablished kinship with trolls like Egill Skallagrímsson). It's a widely-acknowledge attribute of trolls, at least in Iceland, that if you do manage to get them on your side they are loyal, hence the word trölltryggur 'trustworthy as a troll [=extremely trustworthy].'
The alternate way to avoid being eaten is, of course, to pray to [Thor/St. Olav] to come destroy them with his [hammer/axe]. I don't think this throws off what I'm saying here though, because "extreme violence" is also an option for dealing with humans in a reciprocation-exchange relationship too.
Anyway, my point is that the responses to the two different fears are the exact opposite of each other. You respond to the fear of conversion by never associating with trolls, never falling for the deceit that they are persons like you. You respond to the fear of being eaten by trolls by establishing mutual recognition of each others' personhood.
Contrary to popular belief (which says to never accept any gift from the fey under any circumstances), both of these are represented in folklore. Ólafur Liljurós even presents both of them at the same time, and says it's better to be killed than convert.
There's a big gap in this, which is magical creatures that don't want to eat you but which are still dangerous. e.g., an elf is not going to eat you but you still don't want to piss him off because he'll shoot you with a disease-transmitting arrow. But I think this can get filed along with the fear of being eaten, it's just that because the Eduardos (Vivieros de Castro and Kohn) are themselves talking about cosmological food chains, and I'm working from their material, there's better opportunity for examining trolls that eat people.