What's the Name of That Book??? discussion

SPOILER ALERT. The book I am trying to find was from the late 70's or so. I read it between 1978 and 1980. Sword and Sorcery (but I don't think there was any sorcery in it) paperback. I don't remember it as being part of a series. The story revolved around an emperor's son who killed a slave using his fingernails. Once he became the emperor he had the protagonist locked in a dungeon. The protagonist was blinded in one eye and had several fingers cut off, which were then fed to him. His family was killed, and also fed to him, except for one of his daughters. The protagonist eventually escapes and leads a revolution against the emperor. I think the protagonist's name started with a J. It was a pretty brutal book. More in line with Karl Edward Wagner's Kane books than with Conan or any of the more heroic sword and sorcery characters.