Richard Wagner's last opera has remained controversial since its first performance for its unique, and, for some, unsavory blending of religious and erotic themes and imagery. Based on one of the medieval epic romances of King Arthur and the search for the holy grail (the chalice touched by the lips of Christ at the last supper), it recounts over three long acts how a "wild child" unwittingly invades the sacred precincts of the grail, fulfilling a prophecy that only such a one can save the grail's protectors from a curse fallen upon them. Interpreters of the work have found everything from mystical revelation to proto-fascist propaganda in it.