Guess I never noticed the black sludge during any of these later episodes. I'll have to keep a closer eye out for it.
As I said earlier, this makes sense as it is a new writer. Basically the original writer of the show quit after I think season 5 and they got someone new. This new person says they have story for 10 seasons of the show. I tried to find the article I remember reading but couldn't but I did find this one that explains it pretty well. http://screenrant.com/supernatural-s...jeremy-carver/