This review WILL CONTAIN SPOILERS for the episode to be discussed, if you do not want certain plot points or story spoilt, please do not read further.
Supernatural finally gets back to the main season arc this week as the Winchesters team up with Crowley and Rowena (yes, Rowena's back!) to take on Lucifer.
What's kind of surprising about this episode is that after ten seasons with no mention of the Hand of God weapons we get the third one already in the form of the Horn of Joshua. It makes sense that the series has created mystical WMD's in order to take on an enemy like the Darkness, but for these things to be so rare yet pop up again so quickly kind of goes against the notion of them being almost unheard of.
That being said, Crowley manages to track down another of the Hand of God weapons and makes a deal to team up with the Winchesters in order to use it on Lucifer. A lot of the episode is given over to the three of them as they argue over the plan, with Sam and Dean wanting to exorcise Lucifer after he beats the Darkness, and Crowley wanting him dead immediately. When the three of them are contacted by Rowena they realise that they will be able to use her and the codex to remove Lucifer from Castiel and agree to attempt a rescue.
It turns out that despite having her neck broken by Lucifer Rowena is still alive, having used her magical know how to place an artifact inside her body that will repair her body in the event of her death. Guess it's a really good thing for her that Lucifer only snapped her neck rather than exploding her like everyone else.
Getting Rowena back is a fairly unexpected but welcome development. The show has a terrible history as far as killing off side characters goes, and Rowena was such an enjoyable addition to the series that killing her off when they did would have been another mistake on the part of the writers.
Working together, Sam, Dean, Crowley and Rowena summon Lucifer and trap him inside a ring of angel fire, trying to cast Lucifer out of Castiel's body. When things don't work Crowley tries to give Castiel a hand, by going inside Castiel too.
The inside of Castiel's mind and the confrontation that follows is an interesting idea, I love the fact that Cas is just hanging out in the Winchester's kitchen, but Cas just sitting around trying to watch tv whilst Lucifer does whatever he wants feels a little odd. I'd have rather of seen Castiel in more of a prisoner role fighting to get out rather than as someone who seems to have lost all interest in the outside world.
Maybe Lucifer is causing this disconnect in Castiel, maybe he's keeping him in this strange stupor, but if that's the case it's not been explained at all. As it is Castiel seems much weaker as a character now as ht's been portrayed as someone who just doesn't care, which is really not who he is, especially considering the only reason he let Lucifer in was because he cared about beating Amara.
Unfortunately for the Winchesters, the attempt to get Cas back fails, just in time for Amara to arrive. Putting their differences aside for the moment the group gives Lucifer the Horn of Joshua to use on Amara, but the weapon has no effect on her.
Amara captures Lucifer and leaves the Winchesters and Crowley trying to figure out just how they might be able to defeat her.
Despite not a lot happening in the episode (seriously, most of it is Crowley arguing with Sam and Dean) a surprising amount actually happens. Rowena comes back, Lucifer takes over heaven, Castiel is stuck inside Lucifer, Amara withstands a Hand of God and Lucifer is taken captive. With so much happening in one episode and so little time left until the end of the season it's starting to look a little doubtful that the Winchesters are going to find a way of defeating Amara this season. With season twelve coming up, is Amara going to carry across into the next season?