Draugar possess superhuman strength, can increase their size at will, and carry the unmistakable stench of decay. They are undead corpses from Norse/Icelandic mythology, that appear to retain some semblance of intelligence. They exist either to guard their treasure, wreak havoc on living beings, or torment those who had wronged them in life. The draugr's ability to increase its size also increased its weight, and the body of the draugr was described as being extremely heavy. Thorolf of Eyrbyggja Saga was "uncorrupted, and with an ugly look about him... swollen to the size of an ox," and his body was so heavy that it could not be raised without levers.They are also noted for the ability to rise from the grave as wisps of smoke and "swim" through solid rock, which would be useful as a means of exiting their graves. In folklore the draugar slay their victims through various methods including crushing them with their enlarged forms, devouring their flesh, devouring them whole in their enlarged forms, indirectly killing them by driving them mad, and drinking their blood. Animals feeding near the grave of a draugr may be driven mad by the creature's influence. They may also die from being driven mad. Thorolf, for example, caused birds that flew over his howe to drop dead. Draugr are also noted as being able to drive living people insane.
The draugr's victims were not limited to trespassers in its howe. The roaming ghosts decimated livestock by running the animals to death while either riding them or pursuing them in some hideous, half-flayed form. Shepherds, whose duties to their flocks left them out of doors at night time, were also particular targets for the hunger and hatred of the undead:
... the oxen which had been used to haul Thorolf's body were ridden to death by demons, and every single beast that came near his grave went raving mad and howled itself to death. The shepherd at Hvamm often came racing home with Thorolf after him. One day that Fall neither sheep nor shepherd came back to the farm.
Draugar are noted for having numerous magical abilities (referred to as trollskap) resembling those of living witches and wizards, such as shape-shifting, controlling the weather, and seeing into the future. Among the creatures that a draugr may turn into are a seal, a great flayed bull, a grey horse with a broken back but no ears or tail, and a cat that would sit upon a sleeper's chest and grow steadily heavier until the victim suffocated.The draugr Thrain shape-shifted into a "cat-like creature" (kattakyn) in Hromundar saga Greipssonar:
Then Thrain turned himself into a troll, and the barrow was filled with a horrible stench; and he stuck his claws into the back of Hromund's neck, tearing the flesh from his bones...
Draugar have the ability to enter into the dreams of the living, "but it generally happens even so that they leave beside the living person some gift, by which, on awakening, the living person may be assured of the tangible nature of the visit." Draugar also have the ability to curse a victim, as shown in the Grettis Saga where Grettir is cursed to be unable to become any stronger. Draugar also brought disease to a village and could create temporary darkness in daylight hours. While the draugr certainly preferred to be active during the night, it did not appear to be vulnerable to sunlight like some other revenants. A draugr's presence may be shown by a great light that glowed from the mound like "fox-fire." This fire would form a barrier between the land of the living and the land of the dead. The draugr could also move magically through the earth, swimming through solid stone as does Killer-Hrapp:
Then Olaf tried to rush Hrapp, but Hrapp sank into the ground where he had been standing and that was the end of their encounter.
Some draugar are immune to weapons, and only a hero has the strength and courage needed to stand up to so formidable an opponent. In legends the hero would often have to wrestle the draugr back to his grave, thereby defeating him, since weapons would do no good. A good example of this kind of fight is found in the Hrómundar saga Gripssonar. Although iron could injure a draugr, as is the case with many supernatural creatures, it would not be sufficient to stop it. Sometimes the hero is required to dispose of the body in unconventional ways. The preferred method is to cut off the draugr's head, burn the body, and dump the ashes in the sea; the emphasis being on making absolutely sure the draugr was dead and gone.
The draugar were said to be either hel-blár ("blue-death") or, conversely, nár-fölr ("corpse-pale"). The "blue-death" color was not actually achromatic but was a dark blue or maroon hue that covered the entire body. Glámr, the undead shepherd of the Grettis saga, was reported to be dark blue in color and in Laxdœla saga the bones of a dead sorceress who had appeared in dreams were dug up and found to be "blue and evil looking."
The resting place of the draugr was a tomb that served much as a workable home for the creature. Draugar are able to leave this dwelling place and visit the living during the night. Such visits are supposed to be universally horrible events that often end in death for one or more of the living, which would then warrant the exhumation of the draugr's tomb by a hero. The motivation of the actions of a draugr was primarily jealousy and greed. The greed of a draugr causes it to viciously attack any would-be grave robbers, but the draugr also expresses an innate jealousy of the living, stemming from a longing for the things of the life it once had. This idea is clearly expressed in the Friðþjofs saga, where a dying king declared:
My howe shall stand beside the firth. And there shall be but a short distance between mine and Thorsteinn's, for it is well that we should call to one another.
This desire for the friendship experienced in life is one example of the manifestation of this aspect of the draugr. Draugr also exhibit an immense and nearly insatiable appetite, as shown in the encounter of Aran and Asmund, sword brothers who made an oath that if one should die, the other would sit vigil with him for three days inside the burial mound. When Aran died, Asmund brought his own possessions into the barrow: banners, armor, hawk, hound, and horse. Then Asmund set himself to wait the agreed upon three days:
During the first night, Aran got up from his chair and killed the hawk and hound and ate them. On the second night he got up again from his chair, and killed the horse and tore it into pieces; then he took great bites at the horse-flesh with his teeth, the blood streaming down from his mouth all the while he was eating... The third night Asmund became very drowsy, and the first thing he knew, Aran had got him by the ears and torn them off.