I hope you do write more! Don’t know if you have read that ongoing serial story of mine, ‘Caring for a Friend’, over on Archive of Our Own, where I am Tanist? I think the most recently published chapters start the explanation of how I see Onni’s and Reynir’s fusion magic coming to be. I must admit that I heavily mined the our-world folktale of how the extant Nordic pantheon came to be, as a fusion and alliance between the Æsir and the Vanir (the ‘wise Vanes’ mentioned in the rune-poems), who brought their magic to the Æsir as part of the deal, as well as Frey and Freyja as ambassadors. .
And yeah, the Icelandic Seidur (sorry, can’t make that accent thingy work) do strike me as arrogant. They remind me a lot of the attitude of the English folklore collectors of the eighteenth and nineteenth centuries, who were incredibly condescending to a lot of the cultures whose lore they collected. The one that personally annoyed me was the assumption that the mass of traditional songs, music, poetry and epic tales collected from the folk of Wales, Ireland, Scotland and the Isles could not of course have been composed by such barbarians, but must have been composed by somebody civilised, and they were just parroting what they had heard......*grinds teeth*. Yes, I have worked my way through many decades of the Annals of several English folklore societies in search of stories.