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Evil spirits were sent to the Barrow-downs by the Witch-king of Angmar to prevent the restoration of the destroyed Dúnedain kingdom of Cardolan, one of three remnants of the Dúnedain Kingdom of Arnor.

They animated the dead bones of the Dúnedain, as well as older bones of Edain from the First Age, which still were buried there.

The Barrow-wights appeared as dark shadowy figures with a pale, icy light that gleamed from what appeared to be their luminous and cold eyes. Their voices were deep, hollow, and cold; their bony fingers had an icy touch like a deadly grip.

Victims under a Barrow-wight's spell would lose their will; in this way the Barrow-wights drew the living into the tombs of the downs. Some, if not all, victims were laid on a stone altar and bound in chains of gold, to then be draped in pale cloth and jewelry of ancient dead, and killed by a wight with a sacrificial sword. They were also known for carrying rattling gold-rings on their bony fingers.
 
East of the Brandywine River beyond the Old Forest were the Barrow-downs, the most ancient burial ground of Men in Middle-earth. There were no trees nor water there, but only grass and turf covering dome-shaped hills crowned with monoliths and great rings of white stone. These hills were the burial mounds that were made in the First Age for the ancestors of the Edain and later in Second and Third Ages for the Kings of Men.
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In the darkness, wights were powerful spirits, resisted only by strong incantations such as Tom Bombadil's song. Dependent for many centuries on the dark security of burial vaults, they feared the sunlight, and would be diminished in exposure to it.