“Game Of Thrones"’ third season solidified the fantasy drama status as HBO’s second most-watched series of all time (next to "The Sopranos”). But to draw even more viewers in time for the April 6 premiere of the show’s fourth season, HBO has tapped 10 rappers for a hip-hop and reggaeton mixtape, “Catch The Throne,” for original songs inspired by the series and its themes of battles and power struggles.