Francisco Diaz was the sole survivor of Cortes' expedition to Tenochtitlán. He lost his sanity which may have contributed to his survival because the Aztecs believed he was touched by the Gods. He lived in Tenochtitlán for 23 years and imparted his Western knowledge to the Aztec priests. Due to miscommunication and to Diaz's mental state, much of the information is erroneous and bizarre. The priests carefully created several codices containing this knowledge.