Danger from Vega / Clash of Star-Kings

Clash of Star-Kings by Avram Davidson Set during the reign of the Aztecs in Mexico, two alien forces, dormant for centuries, enter a confrontation on a remote mountain that will decide Earth's fate. The Great Old Ones benevolently ruled before the cruel Aztecs were shaped by the Huitzil, who came from the Evil Stars and taught the Aztecs how to conquer and demanded endless human sacrifice. Danger from Vega by John Rackham Flashing across his viewscreen, an iridescent image was Jeremy Thorpe's first glimpse of the Vegans, the mysterious infiltrators of Earth's galactic sector, bent upon a seemingly mindless determination to eliminate the men of Earth. This first glimpse was very nearly his last when Jeremy's ship Quest was almost instantly plunged into the center of a holocaust of heat-beams and fragmentation bombs. Jeremy and the two other survivors of Quest escaped with their lives only to find themselves stranded on the shores of a Vega-occupied planet. And in order to survive they had to discover that the key to Vega lay in the strange magic of a race that seemed to consist entirely of the opposite sex. Shocking stuff!