Okay, so I've been reading this webnovel on RoyalRoad for months now, and the core cast is pretty tight. Elara, the 'Lady Dhampir' herself, is obviously central—half-vampire nobility trying to hold her family's crumbling estate together while navigating court politics where everyone wants to either exploit or exterminate her. Her dynamic with Kaelan, the cynical human swordsmaster she hires (and who totally has a hidden past), drives a lot of the early action. Then there's Silas, her ancient vampire father who's more of a cryptic, occasionally terrifying mentor figure than a real parent. The antagonist you love to hate is Lord Valerius, a pure-blood vampire lord obsessed with purifying their bloodlines who sees Elara as an abomination. A lot of the tension comes from whether Elara will lean into her vampiric heritage for power or cling to her human morality, especially when she starts developing forbidden magic.
Honestly, the side characters sometimes steal the show for me. There's this fae merchant named Corbin who shows up every few chapters with suspiciously convenient magical items, and Elara's few human retainers, like the fiercely loyal housekeeper Marta, ground the story in the daily struggle of keeping the lights on. The cast isn't huge, which lets their relationships develop in a satisfying way without feeling cluttered.