A fan theory that Qhorin Halfhand, the Night's Watch ranger who was killed by the Wildlings, is actually Ser Arthur Dayne, the Sword of the Morning who fought at the Tower of Joy. The theory argues that Arthur survived the battle and took the black to serve the truth of the Song of Ice and Fire. More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.