As I understand it, once you fylgja is unveiled, it becomes a vulnerability because killing it kills you
This is only an issue if you manifest it physically, which you can always just, y'know, not do that. It's dangerous because people get tempted to do that, not because they're forced to.
About that ...
I don't know how much Imperial Fister wants to deal with the impact of Xianxia timescales on animal husbandry, but there's actually a good chance farm animals are ridiculous super-breeds. And that's before getting into the influence of the actual magic in the setting.
This is plausible, but it doesn't seem to have hit how many babies they have in cattle (the cow is only having one calf, after all), so I doubt it's increased that in other animals either. They may well be bigger and healthier (in fact, the cattle provide 12 Food when slaughtered, enough to feed two people
for a year with no other food...that's a lot of cow) and provide more milk (2 Food worth per turn is a lot...probably on par with dedicated modern dairy cows, who produce a lot more than most other cows), and may live longer and similar things, but all those would likely be comparable among different species.
Which is to say they may well be enhanced in various ways, but that's covered by the system stuff, and their breeding rate does not seem to be among the ways in which they are improved.
I can think of one that could work if it's possible to lean more to the underlying themes of our Muna rather their hugareida expressions: hearthfire, the fire of staying safe and warm and cozy and protected with your loved ones. The fire that doesn't want to change.
You're thinking of Campfire and I'm doubtful. Blackhand knows fire like nobody else, if any Fire hugareida could alloy with Standstill he'd be the guy to know, but he tells us it doesn't.
That said, we should grab Campfire and ask. Maybe we can talk to Sten about getting it as a personal action during the raid turns? He's gonna be along and I suspect he has it (given that it's the Fire Hugareida that would aid in crafting). We do want Campfire anyway, and I'm curious how it would alloy with Ignite.
Wouldn't it be more likely that Abjorns Fylgja will be a bear?
Like no offense but mechanically a dog just doesn't fit Abjorn what with it helping tracking which really doesn't seem like a skill Abjorn would have at a high level.
Hound doesn't give enhanced senses, it doubles Intercept dice allowing better protection of other people. It seems pretty appropriate (though so does Bear).