The long running Supernatural series has run for over ten years and a season accompanying each one,so it's only fair that it has gained a large following.
There are many fan theories out there,but this one brought to us by reddit user Soverign87 gives an alternate season ten and an ending to the series.
This will contain spoilers.
So as the theory continues from the end of season nine we start off with Dean as a Demon as the mark of Cain wont let him die, Dean was originally meant to be a vessel for the Archangel Michael , Sam was partially healed by the angel Gadreel living inside of him. As Sam was to be the vessel of Lucifer. Sam now has a small amount of angelic divinity in him. "They both kinda went the other way there." Crowley and Castiel are now basically the leaders of heaven and hell,but it's beginning to be clear that neither of them want it. Castiel believing he isn't worthy to lead hands the reigns to Sam and as he already has partial divinity,he is raised to the level of Archangel with the help of the angels united in heaven.
Crowley who is regularly taking human blood to feel again hands over hell to Dean,as Crowley wants to experience life again and Dean is not only conveniently a demon,he is also Crowley's friend. Now Sam and Dean can never contact each other due to the whole angel/demon situation but they still share their brotherly love. Using their positions they stop the angel/demon war and save humanity,as Chuck/God intended with Michael and Lucifer and they can now finally rest,watching over humanity for the rest of time ensuring its survival.
Now don't get me wrong I love the direction they are going with the show now,but I enjoyed the thought of the war finally ending. Comment below your thoughts!