Disclaimer: I don't own Supernatural.

"Was it all worth it, brother?"

Cas stands in front of one of the many, many identical doors leading to another subsection of Heaven. This one, however, holds a special importance. Beyond it, two souls rest instead of one.

Sam and Dean Winchester.

They didn't make it to retirement age, but no one expected them to, especially not themselves. The hunting lifestyle doesn't allow for it, unless they were to follow Bobby's path and become a hub of safety and information for other hunters. But the need to fight the supernatural with their own hands and save innocents was in their blood, and they hunted until it killed them.

Sam holds his hand out, presumably to shake Cas', flustered and blurting out how much of an honor it is to meet an angel. Cas doesn't bother himself with mortal formalities and ignores the hand until Sam slowly lowers it.

Cas calls him the boy with the demon blood, and he looks horrified. He looks ashamed of it, and he should be ashamed. To have demon blood running through his veins is to be tainted by evil. By darkness.

And it is Cas' mission to push him closer to that darkness.

Sam proved him wrong. Cas thought that he was doing the right thing by following orders and playing his proper role to start the Apocalypse and usher in paradise on Earth. But Sam and Dean weren't having it. They fought tooth and nail against the destiny given to them to the point that they rewrote their own future.

Cas likes to think that he helped. Yes, he let Sam out of the panic room in order to finish breaking the seals on Lucifer's cage, but he also distracted Michael with holy oil using a trick that Dean came up with when they reached the showdown between Michael and Lucifer to give Dean time to try and get through to Sam.

When he opens the door and peers into their Heaven, he sees the scars on their souls from their respective times in Hell. Yet, they still smile and laugh in their memories, unfazed by the horrors they faced in their lives, and in their many deaths.

They're resilient.

Dean is screaming. He knows it's Dean because he senses Alastair's presence close to Dean's tortured soul. It's taking him too long to reach Dean's soul, but he and the rest of his brothers have been fighting with all of their might to reach him before he succumbs and breaks the first seal.

With how heavily reinforced the section of Hell he's kept in is, Cas knows that they won't make it in time. He also knows that, had he been given his orders earlier, they would have been able to prevent the seal from breaking. Still, he will raise the soul of Dean Winchester from perdition because it's the mission he's been given.

He closes the door to Sam and Dean's Heaven, age old shame filling him. He learned shortly after raising Dean that the plan was to start the Apocalypse, and that Dean was raised to fulfill a different destiny.

He was raised only after he broke and became the torturer because the seal needed to break.

And Cas accepted that. He understood the importance of bringing paradise to Earth through the Apocalypse. He played his role, until he was convinced that they should be preventing Lucifer's return, not accelerating it.

Dean taught him that sometimes orders must be disobeyed.

Seeing Dean on the ground after Sam jumps into The Cage with Lucifer is the first time he feels true regret for his actions. Maybe he'd felt sorry that things had to play out this way before, but seeing Dean crushed by losing Sam to a fate worse than death makes him realize that the way he felt before was nothing compared to the guilt that swallows him now.

Cas knows that he shouldn't be alive as surely as he knows that it was God who brought him back. He doesn't know why, but he knows that it could have been no one else.

He heals Dean's face, but that doesn't take away the horror and pain from his eyes.

Later, in the Impala, he rides in the passenger seat. Dean is angry enough that he appears unnaturally calm.

"He brought you back, but what about Sam? What about me? Huh? Where's my grand prize?" he asks. "All I got is my brother in a hole."

Cas made his decision to pull Sam from The Cage after that, and found out later that he failed to bring back what made Sam into Sam: his soul.

But he tried because he learned what it meant to have free will from Sam and Dean. He made the choice to try and free Sam from eternal torment. He might not have succeeded, but he helped. Sam's body returning gave Dean real hope that Sam's soul could be returned, too.

And they beat the odds again.

Cas feels his control slipping away. The power of the souls from Purgatory is stronger than he anticipated, and his vessel is breaking apart at the seams.

He hears Sam praying to him. Offering him help.

After everything he's done to them, the Winchesters are still there to save him if he wants saving. They'll help him get rid of the souls from Purgatory, even though he revealed just how broken Sam's soul has become after his time in The Cage with Lucifer by breaking the wall in his mind.

They'll help him even after he tried to be their god. After he demanded that they kneel before him.

It isn't the first time that his pride has gotten them into a nasty situation, and he accepts that he made foolish choices.

He accepts their help.

They taught him what it meant to have a friend. To have someone he can always count on. They taught him about loyalty, and they taught him that they're stronger together.

Cas starts extracting Gadreel's grace from Sam, but he can't bring himself to finish the task. Sam might want him to, but Cas knows that he won't survive if the grace is completely removed. Instead, he uses the remnants to heal Sam's lingering wounds.

Dean is… somewhere else, but Cas thinks that he should be at the bunker. He never understands the rifts that open between the brothers. For two souls destined to spend eternity in a shared Heaven, they separate a lot. They argue a lot.

But he keeps moving forward and knows that it won't be long before Sam and Dean are on the same page once again.

Meanwhile, he's become a thief, but Sam and Dean need him to survive. So, he steals grace just to keep moving forward. It's an equation that balances itself.

If he is to live, a different angel must die.

He feels like a monster surviving this way, but they all make hard choices and justify the means with the end.

Was this how Sam felt when he was tricked into his demon blood addiction? This consistent feeling of not quite being any one creature, but a monstrous hybrid that shouldn't exist.

Sam and Dean taught him what it means to be human. Like many angels, he had been obedient to a fault, but with that small bit of wonder about what it was that made humans so special to God that the angels were to love them more than Him.

They can adapt to impossible situations and find hope no matter how bleak the future seems. They're imperfect, but they embrace that imperfection and find strength in it. It's angels who are the more imperfect ones. Arrogant to a fault. Blind to truths they don't want to acknowledge. Too set in their ways.

Lucifer has him pressed against The Cage, or the mockery of it that Rowena is using to hold Lucifer temporarily. He promises that he can defeat Amara. That they need him if they want to defeat Amara.

And Cas knows the power that Lucifer holds. He's been on the receiving end of that power in Stull Cemetery, when Lucifer killed him with a snap of his fingers.

"Can you really beat her?" Cas asks.

"I can."

Cas signs away his freedom for the world, allowing Lucifer to take over his vessel. If this is the cost of saving the world from Amara's wrath, then he'll gladly pay it.

Sam and Dean taught him what it means to make sacrifices. They taught him that sometimes he has to give up something for the greater good.

They gave up the chance to have normal lives and stayed hunters for the sake of saving people until the day they died. Bled out together in the middle of nowhere, their bodies left for Cas to give a proper hunter's funeral. No one else would've been able to find them.

And he only gave them that hunter's funeral after he peeked into their Heaven and saw how happy they were. How they'd found a peace they could have never achieved in life. Until he saw that, he'd been prepared to find a way to bring them back.

But it's better for them to stay in Heaven this time. He knows that, and it would be selfish of him to drag them back to a world that's been nothing but cruel to them.

He turns away from the door, beyond which two souls rest that have taught him more than his millennia as Heaven's faithful soldier ever could, to face his curious brother.

"Yes," he says. "It was worth it."

Author's Note: As always, this is a tentatively complete story.