Synopsis of 12×10: Someone is attacking angels in Castiel’s garrison and he may or may not be willing to give his life to stop it.
The episode opens with an angel named Benjamin, who is in a female host, playing a video game at a bar. A woman with an eye patch interrupts the game and attacks Benjamin with two angel blades. Benjamin prays to his fellow angels who were once in his battalion for help, but Eye-Patch kills Benjamin before help can arrive.
Meanwhile, Dean and Sam look at Castiel’s board that is tracking the movements of Kelly Kline while discussing Mary’s solo hunting missions. Sam broaches the subject of Dean treating Castiel coldly over him killing Billie, to which Cas walks into the room and definitively announces that he did do the right thing by saving them and that he did not regret it. Cas stubbornly states that he would deal with the cosmic consequences that were to happen.
He follows it up with his typical Cas deadpan and informs the boys that he has to find his friend, who called for help through angel radio. Sam immediately offers to help Castiel, and Dean begrudgingly agrees to help him. Through the entire car ride, Dean and Castiel passive-aggressively snipe at each other while Sam, ever the peacekeeper between the two, tells them to knock it off and talk to each other. Unable to keep silent Dean makes a snide comment, to which Castiel snaps that Dean doesn’t care about Castiel.
The conversation stops as they arrive at the bar to learn more about Benjamin’s death. The remaining angels from his battalion contact Cas and request that they meet. Cas tells Sam and Dean to wait outside of a diner because his fellow angels wanted him to come alone. Isham and Marbel greet Cas by making it known that they think of him as a disgrace and still blame him for the deaths of Uriel and Balthazar.
Cas replies, “Sometimes doing the right thing requires sacrifices,” which is reminiscent of the same line of thought that has Dean so upset with him. The angels continue to insult and put Cas down as they inform him that they did not think he would care about another murdered angel. Cas endures their belittling quietly and does not defend himself.
While outside, Dean storms into the diner, and the angels are less than happy about having “the apes” join them. Isham resignedly tells them that he has a safe house nearby and Marbel goes outside to be sure that Cas did not lead Eye-Patch to them.
Going back to basic tropes from the beginning of the series, Dean scopes out the pie selection, but stops when Isham insults Cas by telling him that he has “no wings, no home.” Dean and Sam pause and do one of their non-verbal communication, and Sam acknowledges that the verbal abuse that Castiel is going through is wrong. Cas responds in a self-deprecating manner, which causes Dean and Sam to exchange another one of their patented “this isn’t right, and we aren’t happy” looks.
Eye-Patch arrives at the diner and kills Marabel as the other two angels and the Winchesters walk outside. Cas recognizes Eye-Patch and is confused as to why she is still alive as she attacks Isham. Isham is about to gain the upper hand, but Eye-Patch uses her powers and blinds everyone. She clearly states that she is not going to hurt humans and that she is after the angels.
Eye-Patch is revealed to be Lily Sunders, a professor in apocalyptic studies who married an angel and supposedly had a Nephilim that Cas’s battalion was dispatched to kill. Isham kills her husband and walks into the house, as Lily runs to her house to save her daughter. The angels outside hear screaming and assume both Lily and daughter were taken care of, but Isham allowed Lily to live.
Dean and Sam decide to be the two who go after Lily as they are the only two that would survive. During this discussion, Cas asserts that he deserves to die since this is his responsibility. After Dean and Sam leave, Cas uses his powers to heal Isham, despite Isham’s continued barrage of insults and putdowns.
Upon finding Lily, Dean and Sam discover that her daughter was human from a previous relationship and that Isham had fallen in love with her and become jealous of the angel she took as her husband. Jealous, Isham killed her family to watch her suffer, so she was doing the same to him. Dean and Sam have an awkward conversation about whether they believe her and also advocate for Cas by explaining that people change and that Cas has changed for the better. Sam stays with Lily as Dean goes back to Cas after he fails to answer his phone.
Lily explains to Sam that she used Enochian magic for revenge and the admission price was her eye, but every spell she uses burns away a part of her soul. She predicts that Isham will kill Dean and like her, Sam will be consumed by revenge and help her.
Dean arrives at the safe house and explains what they found out. Finally, the two can work together and are unable to be manipulated by Isham. Dean attempts to fight Isham, but Isham sends him flying into the wall before turning and beating an already weakened Cas to a bloody pulp. Dean threatens to blast them away but chooses not to after realizing Cas might not survive the banishment.
Lily comes and the epic battle happens between Lily and Isham. Lily removes her eye patch and says she will never be powerless again and uses a spell that is supposed to keep Isham rooted to where he stands. Isham can move despite the spell, but Cas can maneuver behind Isham and stab him through the chest with his angel blade.
Cas apologizes to Lily and says that ignorance is no excuse for the pains she had to suffer through and he has a lot of amends to make. Cas gives her an option to kill him if she is unable to forgive him, which shows that Cas feels like his life isn’t worth much. Lily chooses not to kill Cas and leaves.
Later, Dean and Sam address that Cas isn’t weak and remind him that he’s strong and he has changed for the better; Cas says he doesn’t regret what he did even if it cost him his life, which has been a reoccurring theme for Cas this episode. Sam asks about Kelly and how he’s going to cope with that because at the end of the day it’s a similar situation involving a mother and her child. Unsure about the situation, Cas replies that he hopes that they can find another way and it doesn’t come to having to kill the child.
The episode ends with the boys all being able to communicate with one another and finally addresses that Castiel is not doing well and needs additional support. The fact that both Dean and Sam acknowledge and address that with him shows good character development as they demonstrate their support by helping Cas. Their presence throughout this episode reminds Cas that he is not alone and he does not have to handle difficult situations on his own. Additionally, this episode subtly moved the plot of the season forward, as well as referencing previous seasons and fan favorite tropes. “Lily Sunder Has Some Regrets” is by far one of the better episodes of the season so far.