When the story of Hernan Cortes is told, it usually follows a certain path: Cortes lands in Mexico at such a time in the Aztecs' calendar and looks enough like their god, Quetzalcoatl, that they mistake him for that god, and he proceeds to conquer Mexico and effectively wipe out their entire race.
When hearing the story, one might respond 'oh, that evil Cortes' or the less-defensible 'oh, those stupid Aztecs'. But here's another way to look at it:
'Well, that's what you get for keeping and selling slaves.'
Meet Malinali. Her pre-Cortes background is cloudy, but we know she was born somewhere in the neighborhood of the year 1500, as a member of the nobility. Her father died when she was a child, then her mother remarried and gave birth to a son. Royal families being royal families, men took precedence, and with a son now in the picture, there wasn't any more political use for Malinali. She was handed off to a Mayan slave trader and forgotten about.
Enter Cortes. Malinali met the Spanish in April of 1519; given the uncertain date of birth, she was either in her late teens or her early 20's. Whatever her age was, she was presented to the Spanish as one of 20 slaves offered as part of the housewarming package. She stood out from the other 19 because of her beauty, and as it turned out, she was also valuable as an interpreter; being sold from Aztecs to Mayans gave her a degree of understanding of both linguistic families (the specific languages were Maya and Nahuatl). Cortes originally gave her to a top lieutenant, Alonzo Hernando Puertocarrero, and then later took her as his own mistress. She was given a Christian name, Dona Marina, and paired with a Spanish priest, Geronimo de Aguilar, who knew Maya. Dona Marina would hear Nahuatl speech, give it to de Aguilar in Maya, and then Aguilar would give the message to Cortes in Spanish.
This did not last as an arrangement. Being now handed off to the Spaniards, Dona Marina would learn Spanish as well. Having done this, she managed to cut de Aguilar out of the equation, and became the sole nexus of communication between the Aztecs and Spaniards. She played this for everything it was worth. 'Dona' was a title of respect in Spanish, which was nice, but nice as it was, it was still a slave name. Slaves don't like slave names. As close as Dona Marina was to Cortes- the two are often depicted together- and in the position of power she had worked herself into, she was going to get her old name back. And not just any old name. She was going to upgrade her old name. She demanded the Aztecs henceforth call her Malintzin, '-tzin' being a title held by nobility- the nobility she used to be before being sold into slavery.
At this point, we should get into her place in history as viewed today. Malintzin is variously interpreted as a traitor, a schemer, a survivalist, a victim, the start of a new Mexican people (she had a son with Cortes in 1522, Don Mahin Cortes), but my reading is this. From her perspective, the Aztecs turned her from a noble to a slave and sold her to the Mayans. The Mayans kept her as a slave and gave her to the Spanish. The Spanish, meanwhile, wined and dined her from day one and placed into her hands more power and influence than she had ever had before. As far as she was concerned, she was just paying back everyone for how they respectively treated her. She was Spanish now.
(Malintzin's story depends heavily on context, and as such lends itself to an endless amount of interpretation; mine is only one possible reading. Some believe she betrayed her own people; some believe she did what she had to do to survive alongside Cortes; some believe she was drunk on power; some think the son she had was the beginning of a new civilization. To get a better picture of her and to draw your own conclusions, the book Malintzin's Choices: An Indian Woman in the Conquest of Mexico by Camilla Townsend should provide an excellent starting point.)
And as a Spaniard, she helped bring down the Aztecs. She knew their language. When they made plans against Cortes, Cortes couldn't understand what they were saying, but Malintzin could. Any plans she overheard were relayed to Cortes and promptly squashed; this happened at least twice, once in Cholula and once in Honduras.
After her part in bringing down the Aztecs, Malintzin receded back into the mists, such that her year of death is even more uncertain than her year of birth. Estimates range the year from 1527 all the way to 1551. A move to Spain is placed between the two ends of the spectrum, as Cortes returned to Spain in 1529, and dispute exists as to whether she went to Spain with Cortes to live out her life, or whether she died around the time Cortes left.
What is known is that he built her a house not far south of Tenochtitlan, making sure that however many years she had left, she was well taken care of. It's not certain what exactly she had, though, beyond the house. There is dispute, for example, as to whether she was given slaves.
If she knew her own history, the smart move would have been not to have them. You never know how they might respond if you lose track of them.