At times, Supernatural's ninth season has felt like a show groping for things it hasn't done before. (Sam already got addicted to demon blood and lost his soul, so why not have an angel possess him?) There have been odd decisions, like that attempted spin-off. But at least the season finale was a darn solid ending.
This season started with both Heaven and Hell facing civil wars, thanks to Metatron casting all the angels out of Heaven and Crowley getting weakened. Both of those subplots had a lot of weird digressions and switchbacks. For a few episodes, we were supposed to care about Bartholomew versus that other guy, and the Reverend Buddy Boyle got a lot of screentime for some reason. And the Knight of Hell Abaddon had all sorts of plans for humanity that never crystalized.
But in the end, the Hell storyline seemed to be aimed at forcing Dean to get the Mark of Cain, which turns him into a supernatural killer with less and less control over his urges. Dean killing Abaddon is just another step on his journey. And the Heaven storyline winds up setting up Metatron as the season's ultimate villain, who wants to be God.
And it all adds up to a rousing chorus of, "Everything is Dean's fault." Dean is the one who wouldn't let Sam close the gates of Hell, because Sam's life is more important than the thousands of others killed by demons since then. If Sam had finished the job, Abaddon wouldn't be an issue. Also, the first half of this season was about Dean getting the angel Gadreel to possess Sam, leading to the death of Kevin and Metatron's untouchability.
In a way, Dean losing his humanity is just a consequence of all the shitty decisions Dean has made since he got back from Purgatory.
But like I said, this was a darn solid ending, which paid off the past year's storytelling in a way that felt satisfying and coherent. Definitely better than the past few season finales.
The episode is mostly about the two angels, Metatron and Castiel, carrying on two simultaneous PR campaigns. Castiel first has to finish winning over Metatron's lieutenant Gadreel (a job complicated by the fact that Dean just stabbed him) and then get to Heaven and win the support of all the other angels, who've been swayed by all of Metatron's fancy promises. Metatron, meanwhile, is trying to convince humans that he's a new messiah — because controlling Heaven and ruling the angels is nothing without human worshippers.
Metatron's latest charm offensive is built around exaggerated, smarmy humility, pretending to be a homeless man named "Marv" who goes around healing the sick and raising the dead. "Marv" becomes a Youtube sensation and then sets up at a homeless camp, where he becomes so popular, the people there kill a rebellious angel for him. As he tells Dean, people don't want cynicism, they want something to believe in. They don't really care what it is, either.
Castiel's attempts to counteract Metatron's lies, up in Heaven, are more complicated. His former lieutenant locks him up, and won't believe him when he says the suicide bombers weren't his fault. She doesn't want faith any more, she wants proof. And somewhat ironically, the proof that Castiel wasn't behind the suicide bombers in his name is that Gadreel turns into a suicide bomber in Castiel's name. And then Castiel, whose earlier attempt to use a 1980s-movie ruse to get into Heaven ("prisoner and escort") failed miserably, uses another 1980s-movie ruse to expose Metatron: he broadcasts Metatron's secret confession to all the other angels, using Metatron's special magic radio.
But first, Castiel finds where Metatron has hidden the source of his power, the Angel Tablet: in his typewriter, of course. And he smashes the tablet, ending Metatron's power and also eliminating one of the most powerful objects in the universe.
It's a bold move to make Sam and Dean almost the side characters in the season finale of their own show, but it's one that pays dividends. This is partly thanks to another bold choice the episode makes: Dean loses the big fight. Badly.
At first, Sam and Castiel lock Dean away because he stabbed Gadreel. But then Gadreel himself confirms what Dean keeps saying: Dean is their best shot at ending Metatron, thanks to the Mark of Cain. When Dean finally goes to confront Metatron, he once again sidelines Sam, knocking him out. And then Dean... gets his ass kicked, because Castiel is too dumb to look for the Angel Tablet in the most obvious place. And just as Castiel finally destroys the Angel Tablet, Dean gets fatally stabbed.
If the goal of this episode was to subvert expectations, then well done. I more or less expected Dean to kill Metatron at the last minute, and then stab Sam as the episode's big cliffhanger. (Dean stabbing Sam is probably season 10 material.)
The other big kicker was Sam doing what he swore up and down he wouldn't do: compromise his principles to save Dean's life. Earlier this season, Dean said he took extreme measures to save Sam, and if the positions were reversed, Sam would do the same. And Sam said no, he wouldn't. As borne out by Sam leaving Dean in Purgatory, Sam not trying to get Dean out of Hell, and a few other things.
But when the chips are down and Dean is dead, Sam goes right to the Demon Crash Pad, to summon Crowley. Probably to yell at him at first, but then eventually to make some horrible deal.
Which brings to mind another way the episode defies expectations somewhat: there's no big talk between the brothers. No reconciliation, no "processing our feelings" moment. At one point, Dean is like, "Hey, I..." and Sam is like, "Whatever, brah. Let's go kill Metatron." Given how the teary "sharing our feelings" moment used to be the lifeblood of this show, it's a gutsy move that the show has basically eliminated it at this point.
Sam is saved from selling his soul, or the Impala (which is probably worth more), to bring Dean back to life. Because Dean comes back all on his own, in the episode's final moment, sold beautifully by Mark Sheppard. Crowley genuinely seems a bit regretful as he keeps insisting that he never lied to Dean, exactly, in describing the consequences of the Mark of Cain. Because the Mark won't just let you go, just like that. As soon as Dean touches the First Blade, he comes back. As a demon.
Crowley invites Dean to go howl at the Moon, a reference back to an earlier diner conversation where Crowley asked if Dean didn't sometimes feel like abandoning the grind of hunting monsters. But somehow I doubt random playtime is what Crowley has in mind: there are hints in this episode that his grip on Hell is none too stable. He says he's kicked human blood, but he's said that before. His masseuse seems a bit worried about his leadership qualities. And he tells Dean that Hell is "complicated."
To which Dean replies, "Shower sex is complicated." And who knows, maybe "Let's have shower sex" is what Crowley means by "Let's go howl at the moon." That's the Supernatural spin-off we all want, after all.