Sastiel is a ship that, as I’ve said before, I have a growing affection for. This is partially because of the attitudes of Sastiel shippers in general- clearly Destiel is the monster ship, and there is just so much more material for the Cas/Dean shippers to cite than for the Cas/Sam shippers that most Sastielers do not even try to compete. There’s a kind of concession- like, yeah, we know that your ship has 200% more backup than ours, but we LIKE ours, okay? So we’re going with this interpretation, because we can, and because who’s stopping us?
Shipping a rare pairing tends to be more about choosing to see something as such. Not difficult, given the chemistry of all the leads- but any possibility of Sastiel was overlooked for a long time, thanks to Destiel taking the fandom by storm after Season Four. But with the latter half of Season Nine there seems to be a shift in focus, from Dean and Cas’s relationship to Sam and Cas’s- First Born was a huge turning point in terms of both mythos and relationships. The grace extraction scene is so painfully personal that it, and what came after, felt like a huge step forward. It’s the point at which Cas understands the cycle of undeserved blame that both Winchesters often put themselves through, but he understands it in terms of Sam, rather than terms of Dean, as was usually the case prior to First Born.
The scene’s also interesting in contrast to the narrative running parallel to it, which is the story of how Dean met Cain and acquired the Mark, and fascinating in its own right (Timothy Omundson! BAMF Dean!). But that’s essentially a huge chunk of well-done exposition. The Sam/Cas narrative in no way furthers the plot, but it serves to check in with Sam and Cas’s mental states at that time. Since Season Nine was heavy on the Dean slant, this was important- but since Cas was Sam’s audience rather than Dean, the dynamic felt new.
Then there’s their rapport throughout the scene. After Cas first sticks the needle in Sam’s neck and Sam has the Gadreel flashbacks, Cas pulls the needle out. When Sam asks him if they have enough grace, Cas tells the truth and says no, though he doesn’t look happy about it; Sam then gets him to put the needle back in. Cut back to the scene from Dean killing demons on Cain’s kitchen table, and Sam is bleeding from the eyes, nose and mouth, and Cas has his perpetually the Winchesters face on.
He strokes Sam’s hair, spawning a thousand fanfics, and removes the needle- and, in contrast to bare minutes before, lies to Sam to protect him, telling him all the grace has been removed from his body. He then goes into the real reason he took the needle out- nothing is worth losing you. And Sam seems to get it- that Cas lied about the grace. Yet he doesn’t call Cas out on it, because he understands that Cas believes what he says, even if Sam doesn’t. So much is left unspoken. Twee food allegories aside (no disrespect to peanut butter, as anyone who knows me can attest), it’s a wonderfully written scene, and a lovely dynamic.
In contrast to that, where Sam is vulnerable and Cas gentle, is the highly badass and shockingly hot ending to Inside Man, once Sam, Cas and Bobby have got Metatron out of Heaven. Sam and Cas are absolutely stone-cold as they take Metatron’s grace, shoot him in the knee, and propose that they- ‘what’s the phrase? Blow your frickin’ brains out.’
They are such psychopaths and I love it to death. Sam and Cas’s relationship really has as many facets as Dean and Cas’s, and only recently did it begin to be explored. I’ve also seen Sastiel shipped by many Samgirls who will advocate most Sam-centric pairings. (Most of which are M/M, too- gender is a nonentity on Tumblr, though if you’re a straight, white, right-wing, middle-class male you better start running.)
These pairings that Sastiel’s shipped alongside of sometimes include Wincest, Samifer, Senny, Sevin, SamJess- occasionally Samelia. I assume that there are Cas fans who ship anything and everything Castiel-centric, whether it be Megstiel, Destiel, Sastiel, Hanstiel or, so help me God, Crowstiel. I’m sure there’s someone. Somewhere.
When it comes to Sam, though, it’s easy to see why some people might be drawn to Sastiel as a pairing. Cas is a semi-permanent fixture on the show at the very least- we can generally trust him to come back even after dying- and most people who’ve even so much as kissed Sam ended up dead (see Jess, Sarah, Meg, Lilith, Ruby, Madison and the girl in the mental hospital in Sam, Interrupted. Lori in Hook Man and Cara in Sex & Violence, neither who were recurring characters, were the only exceptions to this rule. Honestly, I’d cite the fact that Amelia didn’t die as some of the the strongest support for the she-wasn’t-really-real theory.) It makes sense to pair Sam with one of the less destructible characters.
But beneath the practicalities of the ship, there are ideas about faith, and fulfilment of faith. I’ve written here about how Cas struggles to match the Winchesters’ preconceptions of angels and justice and morality. Sam had faith even through the first three seasons, as we discover in Houses Of The Holy, an episode I love (shoutout to Kim Manners! Whoo!). This faith is basically demolished over the course of Season Four, after his first meeting with Cas in It’s The Great Pumpkin, Sam Winchester- and Cas was the catalyst for the destruction of it, starting when he and Uriel proposed smiting an entire town (Uriel, you tease). Sam’s response: ‘But you’re angels.’
Cas goes from cold to warm to cold again at the end of Season Six, breaking Sam’s mental dam in The Man Who Knew Too Much, only to fix his mistake at his own expense in The Born-Again Identity.
Sam has seen Castiel humanised too much to be able to think of him as some great entity, I think, but Cas, by the simple act of changing, and of helping those he wronged- like Sam in TBAI, and Claire Novak- has given Sam a new sort of faith. Angels can change, so people can change; Cas said that ‘the only one who has screwed things up more consistently than you is me’, and if Castiel can fix his mistakes, so can Sam. Cas may not be the benevolent guardian he hoped for, but Sam has learned a lot from him.
And for Cas, Sam is living proof that destiny can be changed; by all accounts he should still be Lucifer’s vessel, yet he ended up (generally) the gentler half of the Winchester duo. First Born showed Sam trying to purge himself of the last remnants of his destiny, the physical evidence left inside him- and Cas refusing to let Sam give his life. Cas said that ‘old me would have jammed that needle in deeper until you died’- which I doubt- I mean, Dean would literally murder him- but symbolically it works. If, previously, Sam had meant something to Cas as a symbol of rebellion against fate, then extracting the grace, which was evidence of destiny, would have disproved the relevance of said destiny. By then, however, Cas came to value Sam as a person, and would rather be divested of his symbol than divested of his friend. The grace remained in Sam; destiny still lingered in his person; but Castiel would rather not be able to cast off doubts about whether they’d really defeated fate in Swan Song, than have killed Sam. ‘Nothing is worth losing you.’
And one last thing: let me just say that while watching Seasons four to eight, I shipped Destiel. Then I got into the fandom, and promply defected to linger round the Sastiel blogs. Destiel is a ship with a lot of support and positivity, but it also has a really ridiculous amount of poisonous wank going round. I’ve lost all interest in it thanks to the fandom. I’m not suggesting other people should stop shipping Destiel; if you’re able to ignore the wankery, great. But I think I’ll stay in the corner with the trashy Sasties. The trashier the better. I don’t judge.