The purpose of Gu Zong seeking out Gu An was to have him write his deeds into a book. Naturally, Gu An did not refuse, after all, it was not as if he were asked to write Gu Zong as the protagonist of the "Investiture of the Gods".
In exchange, Gu Zong would promote Gu An's status to an Outer Disciple and grant him a Medicine Valley twice the size of Mystic Valley.
Half a year later, Gu Yu would bring the items to Gu An.
Writing a book in exchange for a Medicine Valley, Gu An thought it was a good deal, especially since he usually had nothing to do.
That night, after Du Ye returned to the house, he asked Gu An what Gu Zong had wanted from him.
"Sect secrets, are you sure you want to probe?" Gu An asked meaningfully, scaring Du Ye so much that he shuddered and dared not ask again.