He's been such a pivotal part of the show, but his storyline seemingly reached the end of the road on Supernatural Season 15 Episode 18.
We know Supernatural uses death loosely, but there was a certain finality to the scene with Cass opening up about the deal, and, of course, how Dean had been a big part of his time on Earth.
If you watch Supernatural online, you know these characters didn't always see eye-to-eye, but they have built a strong bond over the years.
What made that the supposed conclusion to Castiel's arc so sad is that he told Dean he loved him, and Dean didn't say it back.
Castiel: Knowing you has changed me. Because you cared, I cared. I cared about the whole world because of you. You changed me, Dean.
Dean: Why does this sound like a goodbye?
Castiel: I love you.
Could you imagine sacrificing your existence and not getting a warm response on the back of it?
Granted, Dean was clearly in disbelief at how everything was playing out. Dean clearly understood anyone was fair game when it came to taking down the bad guys, but the final scene certainly suggested this death will have a profound effect on him.
Castiel experiencing true happiness by telling Dean how he really felt made for a poignant goodbye, and it just goes to show how great he was in the end.
His words about everything Dean did being in the name of love were beautiful, but I just wish Dean had a better response to it.
The only good that came from this death was that it wiped out Billie, and hopefully, it's for good this time.
Billie was a formidable foe, but there was so much about this particular plot that felt like a convenient way to drag the stories to the finish line.
Her death was memorable only because of the sacrifice Castiel made to make it happen.
Her time on Earth was running out and she opted to be bitter until the end. The twist that she was mortally wounded was a nice touch, and there were some nice misdirects thrown in there.
Her plan to oust God and take over for him and become the big decision-maker of the world may have sounded good on paper, but she struck me as someone who didn't fully think her plans through.
When you're playing with fire, you need to be able to handle the heat, but she wanted to go out by killing lots and lots of people.
Billie would have been better served on another season. I'm not buying her miraculous return to take over the world and dole out her own set of rules for how it should be run.
At least the brothers no longer have to deal with her, but it does beg the question about where she was sending people, assuming it was her doing it.
The chilling reveal that it wasn't just otherworldly beings, or people who had been brought back to life made things all the more interesting.
Jack and Sam questioning whether other people were missing, followed by the scene confirming as much will go down as one of the best on the series.
It almost made up for how terribly the Billie plot was handled.
It seemed like everyone was in a reflective mood, and Jack continues to be a joy to watch. Given that Misha Collins was describing the episode as "tragic" ahead of transmission, and the beginning featuring Jack being sent to The Empty, my money was on Jack dying for good.
It would have hit the brothers in a big way, but the series choosing to clip Castiel ahead of the series finale had a bigger impact.
We don't even know how Sam will react to the news, but I'm sure he will be cut up, nonetheless.
His relationship with Cass was not as strong, but he did grow fond of him over the years. They've taken down many villains, but now there is so much uncertainty as we head into these final two episodes.
With everyone disappearing, my best guess is that Chuck is still writing away to back the brothers into a corner and strike when they least expect it.
The true test will be whether everyone can be brought back, but it's hard to imagine the series concluding with the world on its knees and much of the population dead, or locked in some mystical prison.
Would the series really write out the likes of Bobby, Charlie, and Jody in such a way? I think not, and there's still a lot that will go down before the series wraps.
For now, all we can do is speculate, and I think the brothers will get a happy ending. I'm not sure about Jack because I have a feeling he will be the key to ridding the world of the bad guys.
As a whole, "Despair" was a decent episode, but it was let down by some convenient plotting. Castiel's death is probably the biggest to rock the series in a decade, but I wish his final chat with Dean lasted longer.
What did you think of all those returns? Will you miss Castiel or Billie? How do you think these final episodes will shake out?
Hit the comments below.
Supernatural airs Thursdays on The CW.
Paul Dailly is the Associate Editor for TV Fanatic. Follow him on Twitter.