The Dead is Rising: Beware of the Draugar

Draugar (being plural of draug) possess superhuman strength, can increase their size at will, and carry the unmistakable stench of decay. "The appearance of a draugr was that of a dead body: swollen, blackened and generally hideous to look at." They are undead figures from Norse and Icelandic mythology that appear to retain some semblance of intelligence. They exist 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. While land-draugar was simply undead with numerous magical abilities, sea-draugar was fishermen who had drowned at sea, thus being denied the privilege of being buried. Draugar are depicted as having either pitch black or pale white skin.

Draugar are noted for having numerous magical abilities, 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.
Draugar are extremely powerful undead and have little to no weaknesses. They are immune to all sorts of conventional weapons. A Draugr must be wrestled into its mound by force, but even then may arise again. The only way to ensure a draugr doesn't come back to a living form is to sever the head from the neck, burn the body and dump the ashes into the sea. For this reason, many Norse warriors were buried at sea on a ship which was burned while sailing forth so their spirits could not come back. The mound would then be opened to "purifying" sunlight.
A Tale of Draugr

Prince Asmund

Long ago, Prince Asmund of Iceland lost his way in a storm while hunting. He would have died, were it not for the kind intervention of Prince Aswid, who took him back to the hall of King Bjorn. To show his gratitude, they became blood brothers and quested to destroy all of those who worked evil. They fought beside each other for many years, until Aswid sickened and died mysteriously. Asmund, respecting his promise, insisted on being buried with Aswid to safeguard his journey to the next life.
Several hundred years later, with Viking society on the brink of collapse, a raiding party decided to raid the mound for the gold within. Lowering down their bravest warrior to the depths of the pit, they fled in terror as Asmund was raised out. He told them that Aswid had risen as a Draugr and came back. He devoured his horse, and his hound before turning on Asmund. Asmund showed them the scars he had sustained at his old friend's hands. They had battled for centuries, Asmund holding him off with his sword, but the distraction of the warrior's arrival meant that Asmund could finally slay Aswid. Tale finished, he collapsed and was reburied by the raiding party, who left the treasures in the mound. Aswid they took out, hacked apart, burnt and scattered his ashes.

The more recent creatures are associated with the sea rather than land. These undead beings were once people who have drowned at sea and have risen from the deep being composed entirely of seaweed. Some have described them as being headless fisherman sailing half a boat or in the form of a living corpse.

To prevent the return of dead Vikings, scissors were placed on their chests along with bits of twigs hidden in their clothing. Their big toes were tied together and needles were driven through their feet to keep them from walking again once dead. 

To prevent the dead from rising people would drag a dead body feet first surrounded by a thick crowd so that the dead corpse did not know where it was going. Once placed in a coffin a special door was bolted on to prevent a return visit. This tradition of burying started in Denmark and spread across Scandinavian Europe.