Complex sentence: The Emperor had long been sick anyhow, and the records indicate that the Emperor's condition began to worsen several days before his death, although the illness could have been caused by poison, administered in small doses over a long period of time.
Split into simpler sentences: The Emperor had long been sick anyhow, and the records indicate that the Emperor's condition began to worsen several days before his death. But the illness could have been caused by poison, administered in small doses over a long period of time.