La Malinche

"Cortés has grown close to a Nahua slave named Malinalli. Though she does not speak Spanish, she does speak many of the tribal languages. She communicates on our behalf, though we can only assume what she is saying."

- Giovanni Borgia on La Malinche, 1520.

La Malinche (c. 1496 or c. 1501 – c. 1529), also known as Malinalli, Malintzin or Doña Marina, was a slave who acted as an interpreter, advisor, lover and intermediary for Hernán Cortés during his conquest of the Aztec Empire.

Biography
After arriving in the New World, Cortés grew close to La Malinche, who had been enslaved. Although she understood Spanish, she did not speak it herself. She did speak many of the tribal languages however, and communicated on behalf of Cortés and his men, who could only assume what she was saying. Through La Malinche, the Spanish explorers gained access to the Chetumal Mayans.

Among the Mayans, the Spaniards found the lost explorer Gerónimo de Aguilar, who could communicate with La Malinche through the Mayan language. As the Spaniards met the Nahuatl-speaking Aztects of Tenochtitlan, she would translate Nahuatl to Mayan for Aguilar, who would then translate Mayan to Spanish for the explorers.

Reference

 * Assassin's Creed: Project Legacy - Rome: Chapter 4 - Giovanni Borgia