"The Raven, Nevermore" is a repeatable quest. Please note, however, that the quest reward can only be obtained the first time round.
* Completing the sidequest "Living on a Prayer" unlocks both "Rivenroad" and "Rivenroad (Hard)" repeatable battles. Please note, however, that no further reward will be issued for completing the former.
Actually my guess now is "The Raven, Nevermore" will reward the horn and the part about no FURTHER reward for completing the former is in regards to the regular Rivenroad fight, if you want a further reward you need to beat the hard mode which will most likely reward the earring.