A family of character from Michael Moorcock's Eternal Champion books. The von Bek family is charged with the guardianship of the Holy Grail. Some von Bek family members are incarnations of the Eternal Champion, but not all of them are.
One of my favorites is Graf Ulrich von Bek, the character in the book The War Hound and the World's Pain. Ulrich is a soldier for hire in what seems to be Napoleonic times. He meets his love in a castle that seems to appear from nowhere. Then, Lucifer appears, telling Ulrich that his soul is his already, but he has a proposition. Lucifer wants von Bek's help to recover the Holy Grail so that Lucifer may reconcile with God.