Title: Something Fundamental
Summary: Dean came back from Hell wrong.
Disclaimer: I own nothing and no one.
Castiel does not always understand Dean.
He is often as not an inscrutable human, for all his blunt honesty. Never before has Castiel felt so frequently at a loss, like he is some innocent, some child, and not the foot soldier of the Lord he knows himself to be. For millennia he has watched mankind avidly. He knows the entire history of the Earth. He had mistakenly thought himself knowledgeable. Prepared. Ready.
Dean Winchester came like a revelation.
He had expected a Righteous Man. A fellow warrior of Heaven. A vessel worthy of Michael. He had expected to reach into Hell and find there a martyr, wrongly condemned for the mercy he'd once shown his brother.
Instead, he had found a brutal, broken creature that had not wanted to be saved.
Most of the time, Castiel finds it difficult – if not impossible – to reconcile the Dean he has come to know with the near-demon he dragged from Hell against its will. Dean may not be a Righteous Man, but he's a good one. He is as fierce and loyal and brave a human as Castiel has ever observed. He is unwavering. He is... beautiful.
Most of the time.
Sometimes, though. Sometimes Castiel catches glimpses.
Famine had been able to see it. The deep, dark nothing inside Dean. But Famine had also dismissed it, deeming it nothing but a hollow core, an empty centre. He had told Dean he was dead inside, and Dean had believed him.
Castiel wonders if perhaps Famine was wrong.
He thinks the reason Dean wasn't affected by Famine's power is because what he wants, what he hungers for, is something different to the mundane appetites and lusts everyone else had fallen victim to. It's something darker, something desperate and dangerous, and Castiel can't help but think of the dimmed, tattered soul that had wanted to remain there, suffering in Hell.
When Castiel hears about Dean killing Zachariah, Dean won't meet his eyes.
Castiel tries to recall if another human has ever succeeded in slaying one of his kind. He doesn't think so. For all the Winchesters disliked him, Zachariah was still a representative of God. An embodiment of light and holy grace. An Archangel, and as such one of Heaven's greatest weapons.
Humans aren't supposed to be vicious enough to kill something like that.
Michael, in the end, does not use Dean Winchester as his holy vessel. Castiel would like to be relieved – and he is, mostly. Dean was not forced to say yes. The Devil was not victorious. The world did not end. Yes, Castiel is most certainly very relieved.
He is also strangely, inexplicably unsurprised.
It could not have been predicted that Michael would forsake his intended vessel, and instead take a poorly suited second-best. Dean, at conception, had been biologically and metaphysically designed to accommodate the archangel. For Michael to refuse Dean...
It would only be done if something had gone wrong with the vessel. Something fundamental, something that was too damaged, too broken, for even the grace of an Archangel to repair.
So no, Castiel does not always understand Dean Winchester. He doesn't have to.
He loves him, quietly, and grieves for what is lost.