In the mid–13th century DR, during a visit to the Astral Plane, Aulagol allowed a raiding party of githyanki to discover his astral projection and to pursue him to the astral portion of the city's elder brain. Soon the githyanki assaulted the city and mortally wounded the elder brain.
Taking desperate measures, the ulitharid Thalynsar transformed himself and several other illithids, including Aulagol, into liches so they could devour the elder brain, preserve its knowledge and powers, and take its place. Successful in their endeavor, the illithiliches formed a Conclave of Elders, with Thalynsar as the most powerful among them. He tried to retain much of the elder brain's knowledge for himself, but the excessive information steadily turned him insane, a trait that Aulagol noted.
Nevertheless, Thalynsar ruled Ch'Chitl for over a hundred years. Finally, around 1370 DR, Aulagol and the other Elders united and were obligated to kill the insane Thalynsar. However, they struggled to lead in his place and divide the elder brain's lore.