"Lily Sunder Has Some Regrets" is the tenth episode of the paranormal drama television series Supernatural's season 12, and the 251st overall.
Sam (Jared Padalecki), Dean (Jensen Ackles), and Castiel investigate the murder, only to see Mirabel killed as well by Lily Sunder, who flees when the Winchesters intervene.
After Ishim defeats the humans, Castiel kills him to save Lily, who is unsure whether or not she will give up on revenge since it's all she's had for over a hundred years.
Castiel apologizes for his role in the death of Akobel and May and offers that if she leaves and finds that she can't forgive him, he will be waiting for her to take her chance.
Sean McKenna from TV Fanatic, gave a 4.3 star rating out of 5, stating: "While 'Lily Sunder Has Some Regrets' had a shaky start, it was a case of the week that wound up having dramatic weight and touched on the larger issues the main characters are dealing with.
What a perfect blend of plot, action, callbacks to previous seasons, history-dependent emotional angst, and setup for episodes to come.
Kudos to Alicia Witt for creating a strong, tragic character in Lily, who I'd love to see turn up again.