A person died long ago and their soul went to Heaven/Hell/Some ethereal plane.
Somehow after years of struggle they find an escape back to the Material World.
What allows that soul to have a new material body?
Is it created somehow? Can it only possess another body?
The world in question has magic to some extent, tho its very scientific. I want to avoid simply saying "Magic" or "Just because". Ideally it will be the "same" body as before death as far as looks and so on, but I'm not opposed a very clever possession or something.