In Scandinavian folklore, a myling (or uburd) is the vengeful ghost of an unbaptized or murdered child.
Etymology
The old Norse "utburd" means "that which is taken outside," and this refers to the tradition of abandoning unwanted children (e.g. children born out of wedlock or to parents who lacked the means to care for them) in the woods or in other remote places, where death was almost certain to befall them.
Origin
In the harsh lands of the North, it was common practice to expose infants in times of want, or when the mother was unwed or when the child was sickly or malformed. These children were generally taken outside to die shortly after birth, and were not baptized. Since they were not given a Christian burial, they could not go to Heaven but were forced instead to roam the earth until they could persuade someone to bury them properly. It was believed that these child ghosts would then haunt the place where they had died, or, as told of in countless stories, the dwellings of their killers.
Description
Ordinarily, an Utburd was invisible, although it's doeful cries often rang out across the stony wastes near the little grave it rose from. But a sharp-eyed traveler who heard the cries might glimpse a snowy-plumed owl, skimming low over the distant tundra, or a black dog, waist-high and shaggy, sihouetted on a far ridgetop. Or beneath a nearby shrub, he might even discern for a moment the phantom of the murdered infant itself, it's tiny fists clenched in pain or rage. People said that, in any of his guises, an Utburd could swell to the height of a cowshed. When it returned to his birthplace to seek out his mother, however, it dwindled to a curl of smoke, able to slip into a dwelling and take shape again with all it's hideous strength intact, ready to savor revenge.
Behavior
A myling was believed to be dangerous and seeking revenge long after his parents were in her grave. Most travelers knew better than to look back, for a glimpse of the pursuing Utburd could paralyze a mortal. They would jump on their backs, demanding to be carried to the graveyard so they could rest in hallowed ground. By a supernatural effect, mylings would grow heavier as they neared the graveyard to the point where the person carrying them would sink into the soil. If one should prove unable to carry an utburd to the cemetery, the ghost would kill its victim in rage.
Powers/Weakness
Water and iron, substances inimical to ghosts, could save a mortal persued by an Utburd. If the traveler splashed into a stream or unsheathed a pocket knife in time, he would find himself alone and unscathed in the silent wilderness. More often, though, another wayfarer would happen upon the body days or weeks later, it's bones crushed and it's flesh shredded by supernatural strength and fury.