The key to this fight is to focus on Svipdagr. The sisters will attack one at a time and only after you stagger him, and since im under leveled only a few things stagger him (combo ender/dauntless shield attack/activating furious immolation). It you hit one of the sisters they might both attack but then one will go back to fighting Atreus/Freya. Once you get down to just the sisters be careful not to hit the one fighting your companion so you can focus on one at a time.

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