Mask of the Sun

The Mask of the Sun was device that could allow its wearer to see into the future. It was (generally) a mask designed to look like a human face, and was made of gold. The eyes were white, until worn, then they became transparent, showing the wearer visions of what he or she most wanted to know. Its origins were unknown, but it appeared to have been first created in the distant future. The Mask, or its analog, existed in multiple timelines. In most known timelines, the Mask was first given to the Aztec in 1325. The Mask guided the Empire to glory until 1519, when Montezuma gave the Mask to Spanish conquistator Hernán Cortés, after mistaking Cortés for a god. The Spanish used the Mask to crush the Aztec. Upon his return to Spain, Cortés gave the Mask to his distant relative, Francisco Pizarro, who in turn used it to conquer the Inca.

However, depending on the timeline, the above course of events could vary. In at least one timeline, both the Aztec and the Inca Empire survived, thrived, and became bitter rivals. In the Twenty-Third Century, the Aztec and the Inca were constantly at war, moving across timelines, and time itself, each trying to obtain one or more versions of the Mask and eliminate the other from a given timeline. There was a third party to this conflict: a time-traveler named Esperanza, whose origins were shrouded in mystery, could appear to those wearing the Mask, and offer very limited help and advice.

Mask of the Sun in "Eyewear"
One version of the Mask of the Sun came into the possession of the Moorish slave Estevánico during the closing days of the Pánfilo de Narváez expedition. This version was a simple pair of eye-glasses Estevánico found by chance. Estevánico used the "eyewear" to lead the survivors of the expedition back to safety. He kept them for the next four years, when the groups finally returned to Mexico City. While here, he was alerted by the time-traveler Esperanza the Aztecs; not the Aztecs of his world, but of another one, where they had 700 years to advance and thrive.

Some months after returning to the city, Estevánico became the property of Viceroy Antonio de Mendoza. Despite this change in ownership, Estevánico retained possession of the eyewear. Mendoza sent Estevánico on Francisco Vásquez de Coronado's expedition to find the Seven Cities of Gold in 1539. The eyewear was stolen from Estevánico on this trip, and Estevánico was subsequently killed. The eyewear was found over a century later by the Tewa leader, Po'pay.

Literary Comment
Po'pay's revolution is the center of the story "Like the Rain" by Jane Lindskold, the story immediately following "Eyewear" in Golden Reflections. However, as Lindskold depicts Po'pay using a conventional Mask, and not the eyewear, it does not appear that Lindskold and Turtledove were building on each other's continuity, and that the two stories do not appear to be part of the same timeline.