Normally, the mortal would be emptied of his soul. His truest essence, which, if the bastard was lucky, would be released to be recycled by the cosmos. The ‘investor’ would then take hold, snuggling in tightly to his host body. At first it's kind of like when you purchase a new pair of shoes. How the hard leather around the opening digs into the flesh it surrounds. Then, after a short period of breaking them in, it begins to only feel uncomfortable when you move a certain way. Soon enough though, you forget that you even have them on. They eventually seem to fit as if you’ve always worn them. The truly unlucky, though, they are left inside. Paralyzed and powerless to do anything but watch their lives be lived by someone… something, else.