Well if there was a quest in Eso, a gothic themed quest where things are differant compared to the typical tropes of Dracula and Ravenloft. Where the vampire ruling is a well loved respected person that protects his people more like Janus Hassildor or vampires in the city are law bidding citizens that don't harm anyone they don't kill innocent people or only feed on the willing or animals. Or a small village with a vampire that protects the villege from evil threats.
The challange is coming up with situlations that involves such a vampire but then coming up with a villainous Van Helsing type but with an evil twist to them.

The Villain would be evil in some form or another. Serves the cause of evil or does evil things even if killing what are typically considered monsters. They themselves are the monster..
Examples
A Vampire Hunter that goes out of their way to kill vampires but this vampire hunter is a serial killer and hunts them because a vampire prevented him/her from claiming their desired victim. Not only do they kill the vampires but they also kill non vampire family members to that vampire.
A Vampire hunter that hates everything undead and vampires especially but has no empathy for victims of the vampire and sees them as distractions or bait. Or kills the victim of the vampire then the vampire right after because just because they want to and because they are black guards.
A Van Helsing type that frames goes out of their way to frame vampires for deaths so they can come in easy with permission from the local government to hunt for actual vampires but also gets thrills from targeting innocent people too then get paid handsomely from the City for dealing with the monsters.
A Vampire hunter that hates good aligned vampires and hunts those excuslivly serving for example like Molag Bal or Dagon or Vaermina. Their sole purpose is not only to kill possible champions of good but making sure what they feel should be champions of evil should be evil and enforcing evil and good or law bidding vampires to them are an abomination.
A Psychopathic torturer that not only hunts vampires but also starves them and torments them for fun. Slowly killing them but targets those vampires that really havn't huirt anyone because they are sweeter to the psychopathic's Ears.

Examples for the Vampire.
A Good Aligned Count that protects his people and makes sure to keep his city safe from monsters. Both supernatural and Natural.
A vampire living out their life without harming anyone.
A Vampire Vigilante that stops crime or goes after criminals exclusively but doesn't necessary kill them.
A Vampire Paladin that uses his dark to destroy or fight evil.
A Vampire novel writer that writes popular books of fiction. But being stalked by one of the Evil Vampire hunter types and she asks the hero/villain to protect or investigate the stalker.

So there are many situlations and many possibilities. Get creative, create a fictional and possible situation and maybe explain the characters their motives how the hero/villian can solve the situation. Make it fit Elder Scrolls and a Gothic theme, Could even include other elements of Gothic if you wish like a werewolf instead of a vampire. There is so many differant creative takes you can take some of them could be villainous types I didn't use as examples.