Khamûl was the Ringwraith who was second-in-command to the
Witch-king. He was also known as the Black Easterling and Shadow
During the Second Age, he fought for Sauron until Sauron was overthrown.
In the Third Age, brought back, he may have been Sauron's chief lieutenant in Mirkwood. After 2951,Khamûl was the Lord of Dol Goldur.
During the hunt for the One Ring, he entered Hobbiton and nearly caught Frodo, the Ringbearer, at Bucklebury Ferry.
After the Witch-king's destruction at the Battle of the Pelennor Fields, Khamûl became the new captain of the Nazgûl. He led as they flew into battle at the Black Gate. All were destroyed when the One Ring which held their forms together fell into the Crack of Doom.