vampire thralls (or familiars, ghouls, enthralled human servants, whatever term you want to use) have so much potential.
i like thralls who are kind of genre-aware. they always liked vampire stories, even before they knew vampires existed. they're probably on the younger side, as far as thralls go. they grew up with buffy or the lost boys or vampire the masquerade. so they know their role in this story, and might even jokingly call themselves a renfield. it's a way to cope, basically, using these stories as a way to give meaning and order to the violent chaos of their lives. be honest: vampires are cool.
or thralls who are operating from an older cultural playbook. thralls who have been in service so long that their human lives took place in a feudal society, and they still see their vampire as a feudal lord to them (and as the last person alive who can understand their cultural background, who knows what it's like to watch society change around you until your own beliefs become retrograde, and you find yourself somehow still living under a political system that no longer exists).
you've also got the classic kind of thrall: someone who wants to be turned. they idolize the idea of vampirism, which inevitably leads to idolizing their own vampire personally (the vampire probably does not discourage this). thralls that are basically inventing a one-man religion around the idea of vampirism as a form of personal ascension. their vampire is definitely going to turn them this year. or next year. or the year after that. or sometime. and when that happens, when they finally become a vampire, the thrall will finally feels powerful and beautiful and safe. and it will justify all of the terrible things they did to get there. right?
but you've also got your thralls who didn't want a lover or a master or a ticket to immortality, they just wanted a place to belong. maybe they never had many enduring personal relationships with other humans, so the opportunity to become part (even a peripheral part) of a secret society most people don't know about really appealed to them. thralls play an essential role in the lives of vampires. thralls are needed. they're needed to do terrible things, sure, but they're still part of something bigger than themselves, and that in and of itself can be rewarding. thralls who wanted a family but found a cult instead.
thralls who love their vampire in a more personal way. if vampires didn't exist, they'd still want to be in each other's lives. they've been together for years, they've watched the world change together, they're each other's closest companions. whether it's platonic or romantic, their vampire is the only person they can trust, and that devotion is returned in full. thralls and vampires who are a little bit obsessed with each other, for better or worse, because of the intense mutual dependency this relationship requires.
or, thralls for whom this is basically just a job. they clean, they do paperwork, they run errands, they find victims and get rid of the bodies afterwards... sure, this is the kind of job where sometimes they have to do things they don't feel good about, but there are a lot of jobs like that under capitalism. they could be working for raytheon or something. thralls that are honestly pretty clear-eyed about the fact that their work enables a serial killer, but they stay for the health insurance, the money, the extended lifespan. it's not personal.
thralls whose vampire is functionally their abusive spouse. thralls who look up "battered wife syndrome" on wikipedia and then quickly close the tab and clear their browser history so they don't have to think about it. thralls whose friends keep telling them to leave, but of course it isn't that simple. if they ever did leave, their vampire could easily hunt them down. its easier, safer even, to just try to make their vampire happy. if that involves accepting the violence inflicted on them and taking part in the violence their vampire inflicts on other people, the thrall isn't actually wrong about the fact that they don't have a choice.
conversely, thralls who have a hell of a lot more power over their vampire than you'd expect. after all, their vampire depends on them: for food, for companionship, for the vampire's only connection with the human world. thralls who like having total control over someone (something) that's bigger and stronger and deadlier than they are. thralls who are willing to abuse that power just a little. after all, they live with a monster. they have to be tough in order to hold their own, right? that makes it justified, right?
can you tell i love a good corruption arc? anyway, i think there are a lot of fun things that vampire stories can do with the concept of a thrall. we should play in this space more.