That looks Like Iceland at the end . . .
Actually, it also looks a lot like the Shetland Islands (and I only know that because I just started watching 'SHETLAND' on Netflix).
And that would be a less-expensive and much closer locale to the production's base in Ireland than would be Iceland.
What is Margrette even doing in the inner circle? She might not be a slave anymore but she doesn't have a function. I mean she's not a warrior, not a shieldmaiden, not related to anyone in camp Lagertha. I don't think she Torvi will turn on Lagertha though.