I've been thinking that a infection based vampire story could be interesting.
Most people who contact the virus/bacteria die.
Only 0.0001% who have blood or sexual contact can survive it, they become "vampires" by symbiotic life with the organism
The vampire live very long (500-800yrs?), maybe even forever?
The vampire is not even remotely indestructible; just strong, fast, smart, and persuasive (pheromones?)
But they are blood thirsty, always needing vast amounts of new DNA to help maintain their longevity, by repairing their own with the new.
Due to the low survival rate, vampire empire building is not possible. There are only ~700,000 potentials in whole world that can survive. But not everyone is exposed to even find the potentials (such a thing would be a worldwide plague), so the actual world vampire population is maybe 35 thousand, a few tens per city of the world. If it came to open war with humans, vampires would easily get wiped out - not just from the lopsided odds, but also the nearly impossibly low replacement rate.
Lonely and living in shadows means picking off undesirables for survival. Over millenia, this behavior has grown into a "vampire culture", those new converts who make disturbance are "disciplined". The culture turns their survival behavior into a religious calling, feeding on only those directly observed doing evil. This explains the protection of the cross myth, if one is so religious as to keep a cross handy - they will often second guess the suitability of the target, or delay the meal to recheck, also maybe related to their religious calling.