There was once a prisoner who was destined to save the world from an ancient dragon using the power of his voice. At the moment before his execution, that very dragon appeared in the sky and brought ruin to the town. Amidst the chaos, the man escaped into the mountains. Seeking shelter from the bitter cold, he made his way up a mountain and into an ancient temple. Deeper he went, drawn by the call to adventure. The walls were shelved with rotten corpses covered in dust and still wearing their armor. The dead were wrathful and protective of their graves. To his horror, they rose and pursued him through the labyrinth with their ancient weapons. The man barely escaped with his life. These gruesome revenants were not mere zombies, slow witted and dull. They were Draugar - filled with hateful strength and magic.
A Draugr is an undead human who was especially mean or greedy during life. In other cases, a seemingly kind person may become a Draugr if something makes them restless during burial. They typically guard their graves but can escape them during the night to torment the living. They appear as a decayed, stinking corpse wearing the armor they were buried in. They maintain some semblance of intelligence and possess evil magic (called trollskap in Norwegian) they can use to grow in size and strength, or to travel through stone. A Draugr will not stupidly pursue any living flesh but may target specific people to torment and they will surely devour livestock. An especially powerful one may be immune to weapons and may drive people insane by the mere sight of them. It takes much more than just fire or a shot to the head to defeat one. When dealing with a Draugr, a true hero may be needed to wrestle it back to its grave.
In the Grettis saga, the hero Grettir faces the risen shepherd Glam. Grettir battles an enlarged Glam and finally gets him on his back, but before Glam is beheaded he curses Grettir:
Hitherto hast thou earned fame by thy deeds, but henceforth will wrongs and man-slayings fall on thee, and the most part of thy doings will turn to thy woe and ill-hap; an outlaw shalt thou be made, and ever shall it be thy lot to dwell alone abroad; therefore this weird I lay on thee, ever in those days to see these eyes with thine eyes, and thou wilt find it hard to be alone and that shall drag thee unto death.