Chapitre 1011: The Drums Of War.

She truly thought that Ragnarok would accept her help. All he had to do was allow the will of the plane to invade his soul through his connection to it. His body would belong to the demon god while his soul would belong to the will of the plane. They would fight for his existence, and whoever wins will become his master.

Ragnarok has a very strong soul, or so she has heard from the fountain of life. His soul should be stronger than his body which will give the Will of the plane an advantage over the demon god So the Will of the plane should win if Ragnarok works with it and is cooperative. He will have to bind his existence to the plane in that case. It is the price to pay for his freedom. 

He won't be a child of the plane like her and he won't gain any other benefits apart from his freedom from the demon god. It should be enough for him since he will be helping the plane. She thought it should have been enough. It turns out that she was wrong.