Wikipedia
The draugr or draug (, plural ; modern , and Danish, Swedish and ), also called , literally "again-walker" is an undead creature from Norse mythology, a subset of Germanic mythology.
The word draugr can be traced to a Proto-Indo European stem * "phantom", from * "deceive". The Old Norse meaning of the word is a revenant.
The will appears to be strong, strong enough to draw the hugr [animate will] back to one's body. These reanimated individuals were known as draugar. However, though the dead might live again, they could also die again. Draugar die a "second death" as Chester Gould calls it, when their bodies decay, are burned, dismembered or otherwise destroyed.
Draugar live in their graves, often guarding treasure buried with them in their burial mound. They are animated corpses — unlike ghosts they have a corporeal body with similar physical abilities as in life. Older literature makes clear distinctions between sea-draugar and land-draugar.