Genesis: In the Beginning

At the end of season five, Sam throws himself in the pit, and in season six, he's rescued. But what happens if instead of Lucifer's escape being through Rowena in season eleven, it was right after Sam's rescue? And what if it was with his fellow angel and worst nemesis, Michael?

Lucifer's on top again, and only the Winchesters and their trusty angel, Castiel, can save humanity from the end of all life as they know it and Dean will do anything to save Cas from making the ultimate sacrifice, even if it requires an unique sacrifice of his own.