Michael Moorcock 
Sword of the Dawn 

Duke Dorian Hawkmoon’s quest to destroy the Dark Empire of Granbretan leads him onto the path of a man who possess a rare ring that allows men to travel through time. Hawkmoon uses this ring to travel to a far future New Orleans, where he must battle the Pirate Lords who possess the Great Sword of the Dawn, which can end the Dark Empire once and for all.