All the unwritten rules of rap say it doesn't happen like this. Yet Killer Mike, a Black man from Atlanta, Georgia, and El-P, a white man from Brooklyn, New York, have transformed what should have been the twilight of their careers as rappers into their biggest spotlight yet. Known as the hip-hop duo Run The Jewels, they have headlined festivals worldwide, become action figures and Marvel comic book characters, spearheaded a worldwide countercultural...