I figure she's the key to something. Blood of one of the Aesir and the High Priestess of Cephiro? All kinds of doors she could open. None of them particularly pleasant.

What scares me is the idea that Akio might set up things so that his ultimate revenge can happen completely posthumously, without any further direct input from himself at all. It's the kind of 'If I can't win this thing I will at least ensure that your 'victory' is nothing but ashes' thing I can see him doing as a last resort.