About Arevald SPOILERS

[Naria]

As far as Shiva being a primal of ice, if you listen to the lyrics of Oblivion it is very clear Ysayle was freezing to death when she had her echo vision of Shiva from Hraesvelgr and experiences fragmented memories of Shiva and then miraculously survives. It isn't strange when she summons her version of Shiva as a primal that Ysayle associates her with ice, or ice with power. Oblivion and certain points in the story where Ysayle speaks as if she thinks she is Shiva reborn and not just a primal host makes me agree that Ysayle unconsciously cast away her own identity in favor of "Shiva" as a way to forget how helpless she was in the Calamity, or of everything and one she lost. This is part of why she goes near-catatonic when Hraesvelgr tells her the truth about Shiva and the war.