On the season finale of Supernatural…
Castiel cares for Kelly.
Lucifer reveals he killed Rowena.
Crowley is alive.
Castiel touches power that came from Lucifer’s baby and it transport him to an alternate dimension.
Crowley offers to help put Lucifer back in his cage and in exchange will seal the gates of Hell.
Sam and Dean go with Castiel to the alternate dimension and discover Bobby alive over there. But the world is caught in a war between angels and demons.
Lucifer follows Sam and Dean to the alternate dimension.
Crowley kills himself to keep Lucifer trapped there and Castiel stabs Lucifer.
Lucifer escapes and kills Castiel.
Mary knocks Lucifer back into the alternate dimension but he pulls her in.
The nephilim is born.