Make sure you set Tom Bombadil on your speed dial.

The barrow wights are evil spirits sent by the Witch-King of Angmar to haunt the Barrow-downs of the former kingdom of Cardolan, Cardolan being one of the Dunedain kingdoms and sworn enemy of Angmar. The wights infested the Barrow-downs in part to prevent the restoration of Cardolan and in part as a **** you from the Witch-King to his hated foe.

In a stroke of irony, the Witch King's barrow wights indirectly led to his own death. When Tom Bombadil freed the hobbits from the barrow wights, each hobbit took with him a blade from the graves of the princes of Cardolan. With one of those blades, the hobbit Merry wounded the Witch-King, providing the Rohirric shieldmaiden Eowyn an opportunity to strike the fatal blow. Thus from their very graves did the Men of Cardolan destroy the chief of Sauron's servants.