With the help of a medicine of his own devising he claims to have lived for hundreds of years. He is more concerned with harnessing the massive power of the Cities of Gold to keep his dying race alive, than he is with gold. But he will stop at nothing to get what he wants, viewing the Mayans as an inferior race.
The Olmecs seek an artifact called the "Great Legacy" in order to power their cryogenic systems, as well as samples of healthy cells from the children in order to combat their mutations and their sterility.
The Olmecs are the descendants of survivors of the global war who hid under their mountain. Only their elite were able to survive, suspended in cryogenic hibernation. The Olmecs do not appear to be human (or if they were once Human, it is implied that they have horribly mutated from the fallout of the nuclear war that destroyed their ancestors); they are short, thin and have pointed ears and enlarged frontal bones.
Their technology is generally inferior to that of the modern age, and they use weapons such as spears and swords. They do however maintain some elements of their advanced technological heritage such as the stasis and medical technology used to keep the elite of the Olmecs in suspended animation until an opportunity arises when they can be revived, powered by what appears to be a geothermal power system. This power system is destroyed in an escape by the children and Mendoza, starting a frantic search by the Olmecs for the fusion reactor core (the Great Treasure) hidden in the City of Gold. They also have a single flying machine that appears to use very similar technology to that of the Golden Condor. However, it is armed with some kind of particle beam or focused heat weapon of great power.Eventually, the Olmecs succeed, at great cost, in taking control of the Great Legacy, but it begins to melt down without the moderation provided by Tao's jar. The resulting earthquakes and volcanism destroy the City of Gold.