There was actually an attempt at a spinoff called Supernatural: Bloodlines. There was a backdoor pilot and.. it didn’t do very well. (It was from Season 9 and its the 20th episode) Its not really the same without The Winchester brothers. It was about monsters and hunters clashing in the streets or something like that. You can pretty much skip this one if you want. However, if you are interested go ahead and see what you think of it.
