Okay revisiting my 4->7->10 theory
Hamr 4 got us blackhand (he speaks the first time on the turn we get hamr 4 same turn as witch ritual but he speaks before we enter the witch ritual)
Hamr 7 is shapeshifting
Fylgja 4 is boon+flaw choice
Fylgja 7 is probably evolved battle form
what about
Hugr 4 let's us put the orthstirr in our equivalent dantian/qi sea area
Hugr 7 let's us start condensing said orthstirr
I don't believe that Hugr 7 would unlock 'Orthstirr Condensation'. We already know what it unlocks--Alloying. (Which is apparently a way to combine multiple Hugareida to gain access to new ones without needing to necessarily get a Muna related to it.) Hamr 7 unlocks Shapeshifting (Which in this case, appears to be redefining how your Body interacts with the rest of reality rather than straight up turning into a wereperson, Abjorn's Hamr is
dummy high and yet he still looks like a human--just a big one, and he has Giant's Blood doing that), and Fylgja 7 apparently evolves your Fylgja into some kind of magical beast instead of an otherwise mundane animal with a gimmick.
The Attributes don't seem to be
directly responsible for Cultivation skills, as we saw that one Fifth Decade Priest who had a Soma (Their Body Stat equivalent) of what, 2? It's not hard to raise your Attributes until they start getting to 4 or so, so the fact he didn't do so suggests that it's not
actually something that comes super easily to them, but he was still a fighter that qualified as being 'Twice as powerful as Halla was', and he definitely had the advantage if we didn't have
just the right tools to counter him and then bring him down before he could recover.
It seems more that Attributes are the equivalent of specifically cultivating aspects of yourself, and the Norse don't have actually that much else to do with their Training Dice without the ability to intentionally Cultivate, so they tend to put their excess dice into their Core Attributes as their most 'Efficient' return on investment, which leads to them having much higher ones on average than their peers. Like most settings too, sufficiently high Cultivation in specific aspects (Like Body Cultivation for instance) unlocks special perks that give you a significant edge on those who didn't go through all that extra credit work, but you can get strong even without it--and most people find a way to cheat the system to get the benefits without putting in the time and effort, either through innate bloodlines or special gear or something.
Which seems to be how our own Attributes work.