Boris seems like a suspicious character. He looks creep and he talks creepy. And he lives within the gates of a castle owned by vampires and he works for them. But why? He is alive isn't he? I would think if he were a vampire himself he wouldn't be able to guard the castle gates during the day.

The first time I played QFG4 and visited the castle, I was 100% certain Boris could kill me if I did something wrong. It was quite shocking to learn that he can't, and that the only thing you can do with him is reunite him with Olga.

I always thought of it as a red herring. He seems like he could be undead, he's actually just a bit haggard from living the bachelor life.

I was surprised too. I thought if he wasn't undead, he was at least thralled by the vampires as their slave. But it turns out

SPOILERS:

He feeling suffocated by his naggy wife left town late at night, and ran into Katrina who told him it's very dangerous to wander the forests at night, and after hearing he wanted to leave his old life behind, she gave him his job.

Though I don't think this was actually mentioned in-game.

It is mentioned. It may be Paladin specific, but I do recall reading the full story.

Yes, it's mentioned in-game. You get a sidequest of sorts to get them back together again, and if you ask them about each other after telling them about each other, you get the whole story.

Wait a minute Katrina gave him his job? But he says that he does not know if anyone at the castle is named Katrina

She didn't introduce herself to him as Katrina; he knew her only as "The Master."

No no no, I never said she introduced herself. In fact I never implied she told him anything personal period, aside from saying "It's dangerous out here, you want a job?"

He likely assumed she was The Master's Daughter (Which was the intended red herring) with privileges. But I never said that she told him anything about herself or the castle. Keep in mind he even admits he knows nothing about them.

He seems creepy because you're racist. :D