[FingolfintheBold]

As for the nature of wights, there are others that could explain it better than I, but see how this helps:

During the long war bettween the Dunedain of the North and the Witch King of Angmar(Lord of the Nazgul), many men died on both sides, good and evil. The Dunedain of that time buried their lords and captains in barrows. There were a great number of these graves in the country along the downs and further north as well, especially after the great plauges that the Witch King unleashed upon his enemies. After a long time, when the wars were over and the dunedain all but extinct, Sauron's power began to grow, and evil spirits of either his making or nurturing came into the barrows and inhabited the dead bones of the forgotten kings. With the spirits came the dark magic of the witch king. Now the evil Barrow-Wights prowell their dark graves, casting a shadow of fear over the lands about, capturing stray wanderers and puting them under with dread-incantations.

We dont know of any physical confrontations with them, but it could have happened, and i can certainly imagine great powers like Bombadil and Gandalf striving with them.