I was gathering alchemy ingrediants south of Windhelm near Bonestrewn Crest when I came across a Vampire Nightstalker and his Thrall. Both were just standing around and neither of them were aggressive. There wasn't any place I could see nearby that they would be attached to. Neither of them had a dialogue tree and would only say random things when I got near them or tried to talk to them. I googled it and searched the forum here but all I could find was information on a mod someone is working on and an incomplete Wiki page. Does anyone know if they are there for a purpose or why they don't attack? They seem so out of place.

Occasionally I find the same thing happening with giants that are wandering around the wilderness of Skyrim. I don't have an explanation, but I'd be willing to bet that it's just due to a glitch or something similar.

It's happened to me a few times as well...

I am stoked...

Happened to me with Forsworn on the road West of Druadach Redoubt.

Happened to me with a small bandit encampment. They allowed me to just pass through their camp without being harmed.

I normally see them fighting a Vigilant of Stendar somewhere. Perhaps it had just finished killing said vigilant and the body was laying around somewhere or didn't spawn due to a bug.

Sounds like a glitch to me although i also notice the vigilant of stendarr part of the story so who knows.