Lohengrin
Lohengrin is a character in some German stories of Arthurian literature. He is the son of Parzival (Percival), he is a knight of the Holy Grail who is sent in a boat pulled by swans to rescue a girl who is falsely accused of murder.  He must never tell anyone his name. His story is a version of the Knight of the Swan legend. It is particularly famous now as an opera, Lohengrin by Richard Wagner (1849).