Great Contagion

During the time of the Shogunate, the Deathlords developed a disease that had never been rivaled in it's deadliness before, and has never since; to Creation's great relief.
A virulent disease that traveled by blood and by lung, the Great Contagion spread a black blanket of death across Creation. Nine tenths of all people and animals perished. There was no cure and no one to burn the bodies. Cities were draped and filled with corpses, and the screams of the bereaved soon gave way to silence.