Responses
Im pretty sure that the duke came up with this plan so that his daughter didnt have to risk her life by fighting. Thats why they kidnapped Grace, put his daughters soul into Grace and summoned another soul to replace her fighting the demon king. I think the plan was always get her body back unless her body died while fighting.

correct me if i’m wrong the original soul of Sellonia is in Grace and the Duke is aware of that and does anyone know what kind of experiment are they trying to do ? are they trying to bring back the original soul from Grace to Sellonia ? I also feel so bad for FL as she really thought the Duke cared for her I thought he got brainwashed too but boom he was in it the whole time