Starting this vampire interest check with a non-vampire plot because nobody tells me what to do, not even myself.
In an undisclosed year, in a remote and pitiless valley, a community of poor villagers shambles out from the scant warmth of their hovels into the glittering morning cold beyond. It's the morning of Wintersiege [name pending]: the first day of winter, celebrated with a feast since before their written history. Each villager offers up what she can to the table—some pickled vegetables, a few of last season's dried sausages, a sprig or two of winter forage—but when it's all come together the "feast" is a paltry thing; a scraping-together of scraps and waste parts; a mere shadow of the glories of past years, but what's more, a portent of fortunes to come. As according to this superstitious people, those who eat little at winter's beginning will be eating nothing by Yuletide, and be food themselves by spring; black, huddled meat and snow-scorched bones, uncloaked by the thawing of the frost, gnawed by things unknown and best left unknown.
Character1 refuses to lie down and accept this fate. A prodigy with her father's musket, she, better than anyone, could brave the woods and the disfigured monsters that patrol them, and return with meat and pelts; return a hero. But the village's soothsayers warn of a nasty blizzard on its way, the likes of which can raisin the eyes and strip naked the bones with its shrieking, whistling breath. And so Character1's father forbids her from going; not even with the village's fate at stake may she sacrifice herself, bravely and foolishly, to the woods. So when over the next week she stuffs her pockets with dried meat, and knits the holes in her capote, and casts new balls for her bullet pouch, she must sneak, and skulk, and raise no suspicions from her doting family.
Once she has prepared, Character1 sets out before sunrise, covering her footprints in the snow's first dusting as she descends into the forest. At one point she has a straggly young fawn in her sights, but when she pulls the trigger, her pan flashes; a misfire. At this point she is beginning to struggle to see, with the air thickening (whitening) in every direction. The fawn bolts; Character1 could make it if she turns back now. Instead she follows the animal.
By the time she's soaked, lost, and doomed, she hasn't seen the deer in over an hour. The snow quickly fills in every track she lays; she can barely see five feet in front of her, making it impossible to detect or follow the marks she'd been leaving behind on the trees to guide her back to the village.
And to cut this story short: with no other choice, Character1 knows what she must do to survive to see her family again. She knows this valley lay to the west of its mountain, and so she walks east. And when the ground slopes and sprawls upward, she climbs. She climbs and climbs until she stands beneath an enormous grey wall, and its massive doors of black iron, both standing indomitable against the battering and braying of the wind. And she screams the words which will change her life forever.
"I am your loyal subject, and I invoke my Guestright."
Yes, the castle has gone by many names in many tongues through the centuries, but always it has belonged to Character1's liege-lords; her masters; the House of Valtrecht. And to shelter from the deafening cold, she must swallow her terror, ignore the hideous rumors she's heard about this cursed place, and invoke the laws of hospitality: which per traditions ancient and unknowable will force the patriarch to open his doors to her, and feed her, and safeguard her from the dangers beyond. There she will meet Character2: the master's son and the frail and dying heir to this gloomy place; as well as the bizarre cast of manservants, soldiers, and counselors who obey his every whim. At least for now, as with a mysterious disease ravaging his brittle body, he is not long for this world, and the dark legacy of this place will require a new heir and steward.
As Character1 repays the debt she has accrued to this family, and their castle (which seems at times to have a mind all its own), will the young heir develop forbidden and doomed affections for her? Will the two dream of escaping together to a place warm and safe and far, far away? Or will the castle, and its dark secret, prove indomitable as it crushes their spirit and devours their every hope?
[So, lots of moving parts with this one, and lots that can be altered too. For instance, I don't mind if we wanna instead say Character1 is an outsider from some other place, maybe lost and desperate, or maybe here with a twisted purpose. Obviously reversing the roles is fine too. As long as the general motif is intact: of an outsider trapped against her will inside of a massive, haunted, seemingly sentient castle with its bizarre and dangerous inhabitants. This one's heavily inspired by Titus Groan.]