One Piece begins with the execution of the Pirate King, Gol D. Roger. His death was intended to symbolize the power of the World Government, but had the opposite effect instead, conceiving the Golden Age of Pirates!
One Piece is full of mythology. What happened in the Void Century, anyway? What about the meaning behind the Poneglyphs? Gol D. Roger plays a massive role in this same mythology and is regarded more as a deity than as the fallible man he actually was. His first mate (Silvers Rayleigh, in episode 400 of the anime) provides us with a differing account of the Pirate King, a perspective not as much concerned with the legend as the man himself.
We learn that Gol D. Roger was dying of an untreatable disease at the time of his execution. He wasn’t caught in the prime of his life, but rather, just wanted to go out with a bang, in the words of Rayleigh, “In the last moment of his life, he (Gol D. Roger) turned his fading “flame of life” into a huge fire that enveloped the world.”