When the First Doctor and his companions arrived in the TARDIS, Barbara Wright assumed the identity of an ancient priest. Although Tlotoxl opposed her, Autloc supported her, even when she tried to end the practice of human sacrifice. Autloc ended up sacrificing his position to help them escape.
As the High Priest of Knowledge, he was one of the most powerful Aztec priests. When Yetaxa was "brought back to life" he loyally served her and followed almost every command. Because of his position, Tlotoxl tried to get rid of Yetaxa without his knowledge, but he knew of Tlotoxl's hatred of her. Later he was clubbed over the back of head by Ixta with Ian's club. Ian was sentenced to death and Autloc proclaimed Yetaxa to be false. Despite this he did not let Yetaxa know of his claim that she was false and continued to serve her. He was confused because Yetaxa was going against the traditions and beliefs of the Aztecs. To rid himself of the confusion, he exiled himself. (TV: The Aztecs)
Tlohtoxcatl later described Yauhtloc as a man with no wisdom, since he could not tell the difference between a foreigner and a god: even when the answer to a question was unknown, Tlohtoxcatl taught, one could not conclude that the answer didn't exist. (PROSE: Against Nature)