This was a reply to an anon ask on tumblr, so that's why it's a little rambling and weird in places; i wrote it all in one go.
Think of this as a prologue. I'll probably be writing more for each individual scenario, maybe one trilogy gets a chapter? I'd have to actually watch the prequels at some point, so we'll see how that goes.
so we know star wars is a "long long time ago" which is part of why star wars is so interesting (normally sci-fi is futuristic and fancy and clean) but let's disregard that and say maybe gabriel just lived long enough, maybe he saw a space age with humanity scattered among the stars and earth renamed or maybe just abandoned.
maybe he jumped ship and landed in an alternate universe. who's gonna find him there, when everyone thinks he's dead and he's like 90% sure that the winchesters are gonna take care of michael and lucifer? raphael will have their hands full, and probably only another archangel would be able to find him.
(don't think i missed his passing comment to Kali in the ep where he died, about checking out pandora - that's the planet from Avatar, also fictional, so who's to say he hasn't done this kind of thing before?)
but also there's the question of WHEN applied to the SW 'verse - prequels? original trilogy? episode 7?
if he ended up in the prequels - let's say Tatooine, because I've read enough fic that I have an interesting idea of how the slaves there live - well, he wouldn't stand for that shit, that's for sure. He'd probably become a power to rival the Hutts, but no one actually knows who he is, so generally everyone is fucking terrified of him-
except the slaves.
see, Gabriel doesn't stand for that shit, and he's had practice at freedom trails. he was in america (probably) during the civil war, you can't tell me he hasn't helped slaves escape before this. and they know it. they know he's safety. the Hutts know it, too, but they can't stop him.
(and if he lived long enough to see the space age, who knows what happened to old human mythology? maybe all the old gods, all his old friends, are forgotten and long-vanished, but gabriel's more than a god, he's still around. maybe he casts off loki and becomes something new that still isn't Gabriel, or maybe he keeps Loki, maybe he becomes a Storyteller instead of a Messenger and keeps all those old tales alive, and while he's at it, says hi to all the new gods as well. new planets, new moons, new constellations = new mythologies; but all that's a whole 'nother conversation)
so maybe shmi finds her way to him, maybe she's realized she's pregnant and she's scared; but would she risk dying with a baby on the way? maybe someone else smuggled her out, maybe Gabriel ran into her in Mos Espa and saw her and realized what was going on and helped her escape himself (I mean let's be honest, anakin is a jesus metaphor and mary's an old friend of Gabriel's, he doesn't want to see a woman in a situation like this).
so anakin is born with Gabriel; if he was never a slave then Qui-Gon never finds him, so what then? (i'll be completely honest, i'm not sure i've ever seen the prequels, and if i did it was long enough ago that i remember basically nothing, so i'm drawing all my information from canon divergent fic) Gabriel probably knows the Force pretty well. he sees what's going on with anakin. and he's probably seen the jedi, too, the council and the republic - well, he's been on an outer rim planet that the republic can't be assed to care about, so fuck the jedi, he's taking care of this kid himself.
(has Gabriel ever had children? depends on how accurate you think norse mythology is in the SPN universe, but he loves humans and he loves kids - he'd be good at it).
i don't know why qui-gon, padmé, and obi wan were in mos espa in the first place, but maybe there's another chance meeting, and gabriel winks at the queen in disguise and gets them what they need because he sees what's going on here, and he thinks it's hilarious that this ~~jedi master~~ doesn't
and basically everything would end nicely and anakin might never become the chosen one, or he might be too fed up with injustice to leave well enough alone and maybe he runs into padmé, oh I'm sorry senator, didn't see you there-
they probably fall in love at some point, if they do meet, and the public of Naboo is half scandalized at their senator's choice of partner, and the other half thinks it's cute and probably philanthropy, but neither of them care (and gabriel winks at her again when anakin introduces her to the family and padmé gapes and anakin's like wait, you two know each other?)
BUT MAYBE NOT. maybe gabriel arrives too late, maybe anakin is already darth vader, maybe the republic has already fallen. where does gabriel show up? if he's jumping universes, i feel like it would be easy to aim for something familiar. humans, lots of them, all in one place.
gabriel lands on coruscant, staggers, looks around, thinks fuck this place, and steals away on a ship going somewhere he doesn't know the name of
he spends a few years adjusting, probably, he doesn't like what he sees but what can he do, he's in hiding-! but. there's a rebellion. he rescues someone from a stormtrooper entirely on accident, he doesn't know anything except that he doesn't like the empire and the empire is threatening this dude (indirectly, but still). he's got power, of course, more than he knows what to do with at the moment, and he flicks the trooper's gun away with a snap and knocks them out and pulls the guy into his house-
and bail organa stares at him, because he's still alive and alderaan is nice, okay, gabriel likes it, it reminds him of europe and he spent ages there back home.
but bail organa is staring at him, and he sees this dude who is so, so much more than he looks, and says, i don't suppose i can interest you in becoming a rebel?
(gabriel is in by the time bail finishes saying 'rebel'. bail spends fifteen more minutes trying to convince him before gabriel finally breaks from his fake emotionless demeanor and starts laughing, and asks him what this rebellion is)
he spends a lot of time at the organa's, after that, and the baby organa (as he refers to leia, which always makes her upset when she gets older) grows up with him as a semi-permanent fixture and family friend. the organas have two kids, actually, the other is actually a cousin on breha's side who was adopted into the family as well.
she and leia both know they're adopted, they get along well, they mess around in big, official rooms while gabriel talks with bail and then gets up midsentence to play with them. breha's there, too, just as pivotal as her husband, and she likes gabriel for the second part more than for what he can offer the rebellion.
and then leia's older, she's a part of the rebellion and she's got plans for something called a 'death star', and she doesn't come home.
gabriel finds her in five minutes; five minutes after they get the notice, anyway. leia looks up sharply, and when she sees who it is her face crumples with relief.
gabriel takes her home, and then he goes back to the death star. leia was taking care of the plans she'd sent away, she was a smart girl. but this battle station was more gabriel's league.
he doesn't find the vent that holds the key to destroying the place. here is what he finds:
some really, truly interesting gossip from eavesdropping on petty officers
the squeaky box robots that clean the floor are incredibly easy to sabotage
darth vader's personal quarters
darth vader's personal line to the emperor
moff tarkin's personal quarters and personal line to the guy who worked directly under the emperor (gabriel discards the second and rubs his hands gleefully at unhindered access to the guy's bedroom)
being gabriel, he immediately makes himself as irritable as possible, without once being seen
(and he absolutely prank-calls the emperor a few times, because it's hilarious. the first time went a little awry though, because geez, that face)
darth vader gets sent back to wherever the emperor is, because the emperor wants answers about how "vader" has been misusing his personal holocom line, and tarkin doesn't have the energy to deal with a petty vader and all this nonsense and things suddenly going wrong-
when the death star tries to fire on alderaan, there are a couple very confusing minutes, and then it explodes, rather abruptly.
vader is not on it.
the rebellion is not disappointed in the lack of a challenge. they're at war, it's such a relief to not have to worry about it they throw a party. gabriel arrives at their base, having gotten directions from leia. she's waiting for him, out on the tarmac by a round ship that's definitely seen better days, and she's accompanied by several other people - a boy, and a scowling man who keeps muttering about having better things to do, and an old man in a robe.
gabriel lands in his stolen ship and pops out. "what'd i miss?"
leia beams and turns to the boy and the old man. "this is my father's friend that i told you about," she says, and then with the air of someone unveiling a surprise present, "he's a jedi"
the boy's mouth drops open. the old man stares. gabriel abruptly remembers what his cover story had been.
this is going to take some explaining.
he could say he doesn't know anything about the jedi because he's too young, but then who trained him? besides, he'd appeared like magic in leia's cell - she's not going to let that go. gabriel resigns himself to a long conversation.
maybe he ends up as a weird kind of rankless authority on the rebel base. maybe they call him a general just to pin him down, but he'd refuse - gabriel's had enough of fighting. but as long as he's with them, their base is impossible to find, and they somehow have just as many supplies as they need, and their suppliers magically start charging less.
no one says it, but everyone knows it's gabriel, even if they don't quite understand how.
luke trains with obi-wan, he learns - eventually he still gets shipped off to dagobah. maybe he still goes to cloud city, convinced his friends are in trouble, and meets vader there - or maybe he goes there with gabriel in tow, because he'd seen gabriel in the vision and thought wait, that doesn't make sense, and dropped by the base just to make sure. but hey, if someone wanted luke on bespin, who were they to refuse?
gabriel knows who anakin is on sight, not because he was ever anakin's father-figure or rescued his mother from slavery, but because gabriel looks at the mask and then looks at the force, and it's just an angrier, more righteous, more pained version of luke.
luke makes bad decisions, they get separated, and it culminates the way it was always going to. luke looses his lightsaber, looses his hand, he falls - and gabriel catches him, catches the 'saber (but he does not catch the hand, because ew)
maybe it goes on pretty much the same from there. the empire falls, vader is last-minute redeemed and dies. it's just much, much easier, because at this point leia is a master of getting gabriel to do what she wants, and what she wants is to win.
and if gabriel is there - he sees them grow, he sees leia and han get married (leia is heavily pregnant at the time and luke is smiling more than everyone else combined), he sees luke start his new jedi school
he sees snoke, lurking, wherever the hell he is.
he's there when ben is born.
is gabriel enough to help ben? gabriel knows a thing or two about darkness, he saw lucifer fall to it up close and personally. he saw vader, he saw the emperor (briefly). ben is only a child.
gabriel's a good babysitter. gabriel sees the hurt on leia's face when ben expresses a preference for him, blithely, only three years old-
he takes a sabbatical. he's too involved. he's never been this close to humans, not in a thousand years and more. he drifts among stars, he checks out a couple new planets he hasn't visited yet - oh, there's luke's school, maybe i should go by and check it out, say hi-
-oh.
oh, no.
—and then, maybe not. maybe he stays. han corners him, says i know a thing or two about leaving, so don't do it, ben loves you, you can't leave.
gabriel stays.
is it enough?
maybe he only comes in when the stage is being reset for the third time, in the darkness of the wings when the metaphorical stage crew is still shuffling around. he lands awkwardly in jakku's sands, he's a shooting star, he almost died and he lies there for days, trying to recover and get the sand out of the stab wound, oh god, lucifer-
a tiny, disappointed voice pipes up, you're not a wreck.
gabriel cranes his neck and sees a tiny figure in dirty clothing and makeshift goggles, clutching a staff that's twice as tall as her and only a little bit thicker than her arms and legs
that's debatable, he says, and hauls himself up out of the wreck. rey's skinny enough that two of her just about equals one gabriel. where am i, anyway, kid?
niima outpost isn't his style. gabriel can't get the girl out of his head - especially not after he sees her with unkar plutt.
he follows her back, and when rey sees him and jumps up to defend her home, he says hey, i brought food.
the portions are as good as a shield. he hadn't stolen plutt's stuff - other people needed to eat too - just made more of it and stolen the excess. rey's eyes go wide.
gabriel doesn't eat any of it. he keeps bringing extra portions, and rey keeps eating them, and after a while stops eyeing gabriel suspiciously while she eats.
it takes her two jakku months (just about forty earth days) for her to notice that gabriel doesn't eat at all.
in the eyes of a jakku scavenger, this makes him the world's best roommate.
so rey grows up, and gabriel's with her, and it's not really a fatherly arrangement because rey has parents already thankyouverymuch, they're just - not here. they'll come back eventually. they have to. she's still there so they have to come back for her.
bb-8, when they are introduced, beeps at gabriel. gabriel beeps back. he's good at imitations, can make any noise he wants despite the limitations of his vessel's vocal chords. bb-8 screeches in surprise and decides gabriel is the most interesting human in the world.
and then - finn, poe's jacket, the millenium falcon is in the sky and rey is insisting that they go back, you don't understand, i have to, my friend is still there, he won't know what happened to me!
except then han solo arrives, and then they're attacked, and before rey knows it she's running towards the rebellion and away from a lightsaber and frightening visions, and there's a figure in black with a red lightsaber-
if this was the gabriel who ran, ran from robbing leia organa of her child's affection - he finds them at maz kanata's, maz is an old friend of his (the closest one he's got to his age) but the place is destroyed, rey was there and now she isn't, and leia organa is staring at him across a pile of rubble.
oh, hell.
the gabriel who crashed knows nothing of leia organa besides what rey has exictedly related of the galaxy's legends - skywalkers and jedi and empires falling under the weight of the Good™. he doesn't find them for ages, he's been looking for rey on jakku this whole time because why would she leave? but rey calls niima outpost when all is said and done, and hangs up when plutt answers, and rigs the holocom system to beep constantly.
did you know, scavengers use a system of taps to communicate, the rare times they work in groups? it's good for sounding out metal, and in those big hollowed-out star destroyer ships, sounds echo a long way. gabriel passes niima outpost, hears them-
that's rey's tune. one two-three-four, one two-three one two-three.
he calls back. he steals the holocom right out from under plutt's distracted fingers and calls back, and he and rey both heave sighs of relief when they see each other.
where are you?
you wouldn't believe - come meet me, you'll need a ship - i have something to do, only i can do it-
i'd believe a lot, gabriel laughs, he's so goddamned relieved, she's alive and rey's really, properly living now. he knew she had it in her.
the first thing rey does is drag him to medbay, to finn's side.
fix him, she says. you did it for me, when i was little, you can fix him.
and then - well, rey has to leave, she's got to find a living legend because she's got his lightsaber and his droid, but gabriel's not exactly going to let her out of his sight again.
the gabriel who crashed lets rey go up alone; and, well, we know what happens from there.
(the gabriel who left, who saw the remains of luke's school and got the before-and-after of kylo ren and ben solo, stomps up there and says you better explain yourself, you jerk, your friend's dead and if you don't get your ass in gear and help save the galaxy again i am going to throw you over my shoulder and carry you down to that ship myself, don't you dare be like i was-)
(luke can't exactly say no to that)