Dean and Castiel do not share a single moment together in Purgatory. They learn that the realm is not so much a place, but an entity. It makes decisions, it changes courses, it conspires against the threat that walks on its turf. Purgatory is an undead corpse, paradoxically striving to survive. And it is in their separation that the two suffer most. It is in the eerie silence in moments of peace, and the all-consuming panic of dying alone in the moments of calamity. It is in the gradual suspicion that the other is dead, the growing fear that whispers cold breaths upon the heart and chill down to the marrow of their bones. Alive until proven dead is already a mantra to Dean- years of experience and heartache has instructed him in the art of morbid, tongue-in-cheek optimism. But thick, dark blood on tree trunks and shredded bits clothes on the snouts of snarling monsters do little to help the dying embers of hope.
Castiel knows. He knows that Dean is alive, albeit struggling, and he knows that all of Purgatory is on a mission to keep the two apart. He knows that the two trail in circles like Moses, like the legs of a compass- forever connected, but doomed to never touch. Castiel knows that Dean is struggling, but managing. He knows Dean is scared, no matter how violently he would deny it otherwise, and that he misses his car, his brother, the dingy motel beds. Most of all, Castiel knows when Dean is gone. When the abysm of black that hangs above Castiel’s head is ripped open, and a flash of light surges through the skies of Purgatory, Castiel knows Sam has done his job. His endless, pain-staking attempts have finally met success and Dean is, at long last, saved. A mirage of a smile graces his tired, dirtied face only for an instant, before the angel continues to run from beasts with gnashing teeth and bloodied nails.
The angel knows other things- that Dean will find happiness and security, regardless of what may come. He knows that of the two of them, Dean was the one who deserved to leave. He knows he will one day be forgotten- that he will slowly but surely fade from memory. That in moments of peril, the Winchesters may mutter his name or wish for his aid- but the mentioning will end, like they always do for the dead, and his footsteps on Earth will eventually be covered by the walks of others. He knows they are best left moving on, and are capable of facing what may come. And Castiel knows that his demise is not short-coming, but will be drawn out as excruciatingly as possible- and he knows, of course, that such a fate is a just one. One must reap what he has sown. If fallen angels cannot suffer in hell, then Purgatory will be his daily damnation. A continuous reminder of what he did, what he had, and who he lost in his own exclusive fall from grace. He knows no songs will be sung in remembrance of him, and he knows children will not tremble at the mention of his name- he knows he is just a number, simply a solider, a memory that will perish into extinction between two brothers, the only two who knew him. He knows all these horrible, painful things and, most of the time, he feels them to be true. But, all the while and despite the better judgement that berates and tortures him to no end, he secretly hopes he is wrong. He knows that he is not.
But there are things Castiel does not know. He does not know that Dean has long-since forgiven him- that in the moment Dick Roman was killed, and the friend that Dean once knew emerged from the insane disguise he once donned, forgiving was no longer a choice, but a reflex. He does not know how much Sam missed him, or how long the younger Winchester rehearsed the apologies he would say when he saved his brother and the angel from the other world and they were resting happily in his home. He does not know, of course, that Dean’s immediate reaction upon waking in Earth was to ask a bewildered Sam where Castiel was. Castiel does not know how Sam’s face fell in despair, or how Dean’s curses filled the silent, mournful room. He does not know the car trips they made or the sigils they drew, he does not know what the bottles of drunk alcohol looked like when they shimmered under the moonlight that peeked through Dean’s bedroom windows. He does not know. He was not there.
There are things that Dean is confidently sure of, though. He is sure that, when the rituals finally worked, he had deserved them for all the goddamn trouble they had caused. And he knows that, though Castiel did not appear before them in that instant, he was on his way. He knows that the opportunity to make up for lost time is now- and he knows that the days to come will be filled with jokes, laughter, and smiling because he’ll be damned if they don’t deserve it by now. He knows apologies will not be eloquent, but they will be spoken. And Dean knows that there is a whole side to the story of their time in separation that Castiel will need to know.
When the skies implode again, Purgatory begins to fall apart. The black veil that separates the prison of monsters from a flawed but yearned for Earth decays and tears like the ripping of weak and aged lace. Castiel watches, then, as the threads stretch and snap, and the ebony vacancy becomes filled with shimmering stars and churning colors. And when the angel is uplifted, raised from perdition by the hands of a very flawed but very righteous man, Castiel knows he was never cut out to be God- God is all-knowing, the purest definition of right. When he stands at the rubicon between Purgatory and Earth, when he plunges into the light and is rushed to the salvation that waits on the other side, Castiel realizes that he, in fact, does not know everything and that the few things he thinks he knows are quite possibly erroneous.
Under the shimmering sky of color and hope, his blue eyes reflect the orbs of light. And the stars gleam back curiously at the angel who made a difference- they are happy, then, to know that they will be watching a family exchange knowings and thoughts and errors. They are happy to watch the human art of love transforming pain into joy. They are happy to watch the Winchester family reunited- happy to watch them embrace. They shine, that night, with a special jubilation just for them.