Lee Sin, the Blind Monk was a champion that appeared in the trailer for League of Legends but was never released. Images and names for his spells have always been in the game files. Riot Games said that he wasn't canceled which gave hope to many that the Blind Monk may come.
He was just featured the latest champion sneakpeak (http://www.leagueoflegends.com/news/champion-sneak-peek-lee-sin-blind-monk), but keep in mind that the patch is on April Fools Day. Is this another prank like the one last year where they announced Urf, the Manatee? What do you think?