Kas!Eddie AU where Kas and Eddie are two different consciousnesses trapped in Eddie's body, one which Vecna planted and the other which is still a clinging mind attached to the brain inside the body which is only half-awake at the best of times.
Kas starts off exactly as the other creatures of the Upside Down, but he's smarter. He stalks the military and the strange car that carries an unfamiliar (familiar?) man who's attempting to map out his dimension. Kas chuckles as the man runs from his swarms of bats, his underlings who follow his beckoning call. (Eddie shrieks from inside, as much as he and Hopper don't get along he still knows the chief, knows that the others had mentioned him in their nightmare realm stories. He hates watching him scramble away from Kas's musings. Hates submitting to Vecna.)
It's only during a patrol around the strange radio building that something inside Kas twists, feels something detangle from his mess of self control and ability to freely think. There's a signal that relays through his mind - where his Master's call should reside - that sounds comforting. It's a warm voice, faintly audible beyond static. Then it plays this overwhelmingly wonderful music straight into his head and Eddie twists to grasp some control over his own body as large wings flutter gently to have them land within the radio station. The sounds get louder and they sit there for a good hour just listening to Metallica in their mind. (Kas purrs at the warm voice that breaks in between songs, so much friendlier than his Master's demands. Eddie gags and has half the mind to think some awful retort about the name of Vecna right back at Kas. Kas finds this confusing.)
Later, Kas gets to meet the source of that voice. Steve smells of a beautiful thrumming iron beneath his skin and flesh, and there's a strangely safe aura that surrounds the human who set foot into his realm. Eddie beams happily at the familiar face (and the others, too. Despite how horrified Dustin looks at what they've become. Despite the lack of control and the blinding press of Vecna into their skull which wants them to killkillkill). They can only spend a few fleeting moments before skittering off, Kas taking to the skies and pulling his winged army away with him. Theres a sadness that aches in unison with the hurt looks on the groups' faces, but they can't stay with them. Not yet.
Eddie wakes up more as they talk. Kas isn't much for human words but their thoughts can still be mutually understood inside their mind. Eddie tells him about how awful it is what Vecna (not a "master" of anything, who has no control over Kas) is trying to do to everyone, to Steve. (Something hisses possessively in his chest, and Eddie nods in a disdained agreement. How strange it is, to fall so fast.)
((How strange it is, as well, to find something like that in each other. Familiarity and protectiveness, even if they only exist within the other's head. It's them, after all, they will always have each other at the end of the day. Kas sometimes wishes he could curl around Eddie and hold him safely beneath his wings like he might be able to do with anyone else, but he can't, so instead he curls up in his nest around the body they share while Eddies assures him that they'll figure something out.))
Kas figures out how to let Eddie have control the second time they come across the group, letting his body go loose as the other conscious makes decisions instead. It feels weird, but Kas doesn't mind it. It feels less demanding than Vecna's orders, more like taking a rest back in his nest after a long patrol. Eddie catches up with the others and explains their situation, Dustin in particular lighting up with curiosity about their body-mind situation. Begrudgingly, as Vecna begins to press at the corners of their mind, they hug and say their parting words before heading separate ways. (The party no longer has to be concerned with the bats, They agree. If They can help with anything, it's that.)
There's planning, lots of it. And stolen kisses, as Kas possessively curls around Steve and drags him away from the others where They have the chance. He turns to goo with the human's affection, and Eddie seems equally happy with Their arrangement. Kas thinks them something like the mates he sees amongst his bats, but Eddie chokes out something about phrasing with the term and requests They use the term "partners" instead. Kas accepts this term, as long as it means They both get to protect and love the human as much as They like.
They manage to help defeat Vecna, Kas's trusted right hand position letting Them give the others a head start. (Eddie muses something about Kas the Betrayer in their mind as They take out an eye and an arm. Kas doesn't understand, but he preens under the praise from the party when everyone regroups.)
Kas is afraid he'll disappear in the after, scared he'll vanish with the rest of his realm. Everyone comforts him in the moments it takes for El to close the gate and seal away his world (and potentially him) for forever. He doesn't, though, instead opening Their squeezed shut eyes to the same image that met Them before. There is both celebration and sadness that he feels from Eddie, and Kas understands. This isn't his body, this is Eddie's body where Vecna put him. But Eddie reassures him that it would most likely be even more weird if Kas vanished, so they make do. (The wings get smaller, as do the claws and tails. More manageable, slightly more human. They can no longer fly, wingspan too weak. But that's okay. They're still here, that's all that matters.)
Steve happily accepts both of Them. Loves Them equally. He falls harder every day for Eddie's fun charms and they share their human affections. The human also indulges Kas, lets him curl up around him and kiss him till neither of them can breathe and shadows them in the darkness of Their wings. He says that there are subtle ways to tell the difference between Them before any real confirmation is made. Kas's eyes constrict differently to create a slight murky red, pupils always dilated and facial expressions more subtle. The way Kas holds Their body is apparently different too, more loose and fluid, less fidgety. ("Animalistic, but not in a bad way." Steve says to him one night. Kas understands, and then wraps himself around Steve so he can bury his face in the other's neck. It earns him a chuckle and a delicate hand in his hair.)
All the kids are a hard adjustment. At first, some of them poke and prod and question now that the fighting is over. But then it settles, and they settle into a flow of accommodation for Kas's slightly different needs and Eddie's lack of constance presence around them. (Sometimes, They slip during one of the kid's games, and it causes a funny moment between them all.) At one point, Mike tries to make the connection that Kas is something like a pet, but that word gets Eddie, Steve, and Dustin all equally riled up about his intelligence. Kas doesn't understand what it means, but Eddie and Steve assure him later on that they think of him just as equally as they do of each other. He preens with that notion, loving them both the same.
turnnoffyourmind
snowghoul
andulkaphoto
tangentwithtanner
