The Pines Hunters

Six years later (from the ending of Gravity Falls) the Pines twins are back in town, but know with knew knowledge. There is a lot more out there than what Ford had discovered. And the twins took it upon themselves to protect the people and hunt the supernatural. When they get back to Gravity Falls they see that they are not the only ones who have changed. Wendy and her gang are hunters, Gideon has some sort of deal with a demon, and Bill is back and more powerful than before. (This is a Supernatural and Gravity Falls crossover, sort of, that takes place six years after Gravity Falls.)