From Halopedia, the Halo wiki
During the San'Shyuum's war with the Sangheili, GuJo'n's purpose as diplomat was simply a sinecure position, having been deemed only theoretical. At the conclusion of the war, which ushered in a new age and an alliance with the Sangheili, GuJon's status was renewed and he served as Minister of the Ministry of Kindly Subjection.
In 851 BCE, GuJo'n covened with Mken 'Scre'ah'ben and Qurlom, the Ministers of Relic Safety and Relative Reconciliation, respectively, to discuss the heretical insurrection of Ussa 'Xellus. GuJo'n advocated that the matter would best be handled by the Sangheili loyal to the Writ of Union. They then met with Viyo 'Griot and Loro 'Onkiyo of the Sangheili treaty commission and inquired them about quelling 'Xellus' rebellion.
List of appearances