Ralsei is a fake prince keeping the vessel locked up and separated from the soul at the request of Kris. None of the depictions look like Ralsei in the slightest and there's a reason the town is named after us.
The prophecy simply has no place for Ralsei, it never had. He was intentionally placed by Kris to convince the Soul of cooperating.
This was my retarded theory for the thread, I hoped you enjoyed wasting your time reading it.