Introducing one of the enemies to the game...
Draugr - live in their graves, often guarding treasure buried with them in their burial mound. They are animated corpses with a corporeal body, unlike ghosts, with similar physical abilities as in life.
Source: Wikipedia
What happens when you kill it again? Do they go to Valhalla or they went back to where they came from? I was under the impression that Valhalla needs any warrior fallen in combat. After all, there is more gold in Valhalla then in their graves