I'm guessing dude in the basement is fenrir?

I think we're all trying to figure it out at the moment, however my current theory is basement guy = fenrir = spirit form of the grand duke. I think this because Jarn also seems to have a spirit form that he is unaware of that seems to have shown itself to the grand duke.

Is his aunt also a spirit form or a real person?

Also its hinted they have a previous life together

Thank you for taking the time, I appreciate you