Someone mentioned that it might be about the fall of the Catholic church. I'd have to agree. The Catholic Church had a major role in medieval politics, which could explain the line "I used to rule the world". "I used to role the dice" may refer to the risks the church took in politics, which "Listen as the crowd would sing 'The old king is dead, long live the king!'" could refer to the church standing by as new kings came to power and then died. "I know Saint Peter won't call my name" might be a hint that the practices of the church were never completely saintly. "It was the wicked and wild wind, blew down the doors and let me in" could be something about the turmoil in the middle ages. The religious imagery throughout the song would also lend credence to this explanation.