Welcome to Season 5, where every angel suddenly has a sword with zero explanation! That sentence sums up my general feelings about season five in a meta fashion. It’s all very Chuck.
Dean is having a really hard time dealing with the fallout of s4-- the devil’s on the loose, and it’s all because he failed Sam, and because Sam basically renounced him, trusted a demon more than him...
Sam was manipulated all last season into Doing The Thing He Did, so convinced of his own power, his own righteousness, thought he was saving the world instead of damning it... and explained away Dean’s hesitancy at all of it as “weakness.”
Cas is resurrected for the first time and is “cut off from Heaven,” gradually falling closer to humanity, and also slowly realigning his faith in his terrifying new reality.
and a bunch of other stuff! lol... it’s a season premiere, there’s lots of stuff... Becky the Really Unflattering Fan Avatar (who was more “the fan Chuck chose because her understanding of the line between fiction and reality was just as askew as Chuck’s was and that suited his purposes”), Nick the vessel of convenience for Lucifer, the return of Meg, Bobby paralyzed and in the hospital after stabbing himself to save Dean... so much... maybe a little too much...
Here’s some links that may be of interest:
The Superwiki page for this episode
Lizbob’s Dean and Cas Are In Love series posts for this episode (part 1) and (part 2)
September 2017, notes on retcons, destiny, and free will