The context, as far as I can recall, was what someone would sell their soul for, regardless of the consequences. There really wasn't a basis for how it was done, such as calling upon a demon and going to Hell if you sold your soul, or if your soul, instead of taking its natural course after death, ended up in some other circumstances/condition.
Besides, it's my job to make things more complicated. Don't put me out of work... Please? *Gives the googly eyes of DOOM*