Cortes could only speak Spanish. Therefore, he was dependent on local translators to communicate with the local people. When he arrived on the Mexican coast he was offered 20 slaves by a local leader. One of these slaves was known as Malintzin. She had been baptized as Marina. Malintzin served as translator, cultural advisor and negotiator for Cortes. She had a remarkable ability to learn new languages She stayed by Cortes' side from 1519 to 1526. Malintzin is said to have had a child with Cortes, as well as giving birth to another child with the Spanish conquistador to whom she was married. She died you in 1527 at the age of 25.
Fuller Biography of Malintzin (Women in World History)