I've rearead this series multiple times since many years ago. It seems clear to me now that Odin's doll of salvation is the Nameless Knight who carries his sins. The princess is just bait (although it is diabolical how she can forget him so easily). Furthermore, the princess seem to give inmortality, so the Knight/Demon Lords lives forever being cursed by the sins of Odin and that way since he doesn't die the sins don't go back to Odin who is actually alive somewhere