On to lore and the good old reader insert!
Okay, so, the Y/N of this world. Adorable sweetheart, but don't cross them. Fucking loyal as all hell. Jump on you and claw your eyes out level stuff. Though that's only if you unlock their secret boss phase. 99.9% a silly, goofy, playfully teasing cinnamon roll. Whom is married to Onyx. They love this man like the Earth will implode without him. He's very sweet with Y/N, and matches their spirited nature with witty comebacks and the occasional mischief of their own. Healthy relationship ftw [for now >:)]
Sarai and Jex are off living together in the city. Despite each of their appearances, Sarai is actually the one more likely to roll up their sleeves and get to work. She manages a pet store, cause she's a big baby for animals, will absolutely not stand for it if even a single fricking fish dies under her watch. Can be a bit of a brat sometimes, and rub people the wrong way, but is too stubborn to back down unless it's made fairly obvious she's in the wrong. Always a strike to her ego, though. Jex, on the other hand, is a person with little shame, rather blunt and distant. Which is ironic since they're a selective mute (save for rare occasions with those they're closest to, think a Ferb situation). Gets their point across with pointed looks and hand gestures just fine. Operates as an independent accountant and IT agent, makes a nice little sum for the two of them to live on, especially during tax season.
They tend to have family get togethers at least twice a month, if not more. Depends on each person's schedule. Sarai likes to tease Y/N about their wardrobe a lot, cause their favored colors are closer to Sarai's color schemes. All of them know neither of them mean anything by the biting remarks they exchange. Jex is extremely comfortable around his in-law, having been the first to take a liking to them after Onyx and Y/N started dating. Sarai was...a process, but they got there!
As for Graphite, well, I'm still debating on their role. Tbh they out of all of the others are the most random, and kinda spawned when I was playing around with Sarai design ideas. It's already pretty obvious they're a free-spirited artist, do a lot of tagging in areas they consider drab around town. Thought it might be cute if he came to have a crush on Sarai and will visit the pet store often, seeing another wild child spirit in her like they have. Sarai is heavily amused by her, and will casually flirt with them, not exactly disliking them, but isn't sure about getting into anything actually serious. Graphite might play a later role due to some of their beliefs and the type of things they're into as a result, but we'll see.
The plot is pretty slice of life....until it isn't. You know I can't resist fantasy/supernatural shit. The whole idea that started this entire world spawned from it, really XD Ya see, there's been a little (not actually, definitely not actually) someone watching Onyx and you. Someone not of this world, and kind of not of this universe. An eldritch deity whose name a mortal tongue would never be able to pronounce, but it introduces itself to you as Spheris for simplicity's sake.
The kicker is how it made itself known to you and your husband. Which is by, ya know, possessing Onyx and basically binding itself to him as a vessel. It's kinda like a symbiote from Spider Man thing, though there are key differences, including that Onyx can't just remove and ditch Spheris that easily. And honestly, these two are terrible for each other. Spheris is definitely a big time ass whom normally doesn't care much for the worlds it has come to inhabit throughout its looooooong existence. Occasionally, it will possess a vessel (such as in Onyx's case), if they find it interesting enough, or bestow its gifts to mortals that please it. Both of which are very, very rare, this thing is picky as hell. Anyway, Onyx and Spheris are near opposites, and it results in them becoming increasingly unstable and obsessive. Not that Onyx would ever let himself or Spheris (intentionally) hurt you (which is a bit nuanced cause of mixed emotions and Spheris technically having a thing for you too as a result), it just leads down a bit of a rabbit hole you end up having to escape from.
Sarai and Jex have no fucking clue any of this is happening, but are becoming a bit worried about how distant you two have been acting, their visits to your house dwindling at their sibling's insistence. Of course, they're the first ones you run to, and it becomes a bit of a game of cat and mouse, trying to figure out how to fix things while Onyx is coming after you. There's a lot of complicated feelings about what went down you know you're gonna have to sort out later, but for now the main objective is kicking eldritch ass.
And that's pretty much what I have thought up so far XD It's been a blast, and boy, if I didn't already have a thousand more projects waiting in the wings, I'd be hardcore tempted to write more. *Sighs wistfully* Maybe one day. Hope you enjoyed it for now though!