Okay But The Thing Is That Cas Cradled Dean’s Soul When He Saved It From Hell, Not His Physical Body.

Okay but the thing is that Cas cradled Dean’s soul when he saved it from hell, not his physical body. So while there was a brand on Dean’s shoulder that didn’t end up being permanent, there was a permanent brand of Cas’s grace on Dean’s actual soul. And as they got closer and grew together, it became less of a brand. Dean’s soul fully integrated Cas’s grace and made it a part of his soul instead of a separate thing.

And so Cas confesses and the empty comes and takes him but something is wrong. Because it has Cas, wrapped up nice and tight, but there’s— there’s something missing, something askew. The empty can’t put Cas fully to sleep the way it wants and it’s left with him awake and annoying, just like before. And it tries, god does it try. But because a small piece of Cas’s grace remains outside of the empty, embedded in Dean’s soul, it’s unable to gain full control over him like it wants.

And while it seems like Dean had been unaware of this the last time Cas had made a trip to the empty, he may have figured it out this time. Or he’s just clinging that desperately to his memories of and feelings for Cas, because both Cas and the empty feel continuous tugs on the grace, starting at the part that has made itself a protective shield around Dean’s heart.

And sure, the empty would be thrilled to just swallow Dean and the remaining piece of grace up, too. But it can’t, because Dean’s soul can’t exist in the empty, and Cas’s grace can’t be extracted from Dean’s soul. And with every tug, Cas seems to grow bolder, more confident. Because Dean isn’t letting their bond weaken, despite everything. Dean isn’t giving up hope, they can both feel that, so Cas won’t either.

So at some point the empty has to choose: put up with Cas forever or give up on Cas forever. Because it will never be able to fully own Cas, even after Dean is dead. As long as Dean’s soul continues to cling to Cas, he will never belong to anyone but Dean. So the empty throws in the towel, gives up, and tells Cas to never come near it again. Go the hell away and never come back. And Cas is all too happy to oblige.

The empty doesn’t even bother keeping Cas’s grace and returning him human because that small part inside Dean is more powerful than expected and there’s no saying if Cas would even be truly human anyway.

Dean’s sitting in the war room of the bunker, eyes closed with a hand pressed over his chest, when Cas pops back in. The empty spits him out much in the same way it ate him up and suddenly he’s just standing there, staring at Dean and a wide-eyed Sam.

“Holy shit.” Sam mumbles, staring at Cas as if he’s a ghost.

But Dean doesn’t look surprised at all. “I knew it.” He says, then he repeats it with more feeling. “I fucking knew it! I could feel you.” He taps his chest. “Here. I knew you weren’t gone.”

“I can’t believe you were right.” Sam says, but his disbelief has turned into a smile.

“I told you.” Dean says smugly as he rises from his chair. “I told you that he was going to come back.”

Sam stands too, beating Dean to Cas and wrapping him up in a hug. “He wouldn’t let go of you.” Sam murmurs into Cas’s ear. “He refused to budge even an inch.”

“I could feel it.” Cas answers, and then he taps his own chest as Sam pulls away. “Here.”

“Goddamn right you could.” Dean shoves Sam out of the way unceremoniously before reaching out to grab Cas by the face and pull him into a searing kiss. “Don’t ever pull that shit again.”

Later, after some twenty more kisses, Sam manages to ask what the hell actually happened. He asks how Dean knew, what they could both feel. And Cas explains— talking about his grace and Dean’s soul and how the bond they shared deepened into something entirely different. And he’s warmed from the inside out the whole time because Dean stands firmly at his side, a soft smile on his face as he rubs his chest and if he’s intentionally infusing warmth into Cas’s grace.