Okay so iv read that there's a guy who goes from town to town and rather takes people or kills them... So far I haven't seen him or noticed anyone missing. Does he still appear if your on the vampire side and what does he look like so I can look out for him

I seen him in winterhold he was with 5 other master vampires but im playing on my dawnguard guy

I've never personally seen them, I sided with the Vampires and finished the MQ..I see random vampires in the wilds but they are passive to me.

Dawnguard attack me in the cities and wilds though.

im going to assume he only appears for people who sided with dawnguard because as a vampire i have never seen him.