Topau was the builder of the temple that held the body of the Aztec Yetaxa. By one account, he was the father of Ixta; (TV: The Aztecs) by another account, he was Ixta's grandfather. (PROSE: The Aztecs)
Topau was in love with Cameca, but he disappeared, taking the knowledge of the entrance to the temple's tomb with him. When Cameca stated that he watched over the temple every day, the First Doctor assumed that he was a gardener. (TV: The Aztecs)