When Byleth took on the role of archbishop in Rhea's place, he devoted himself to official business as the new leader of the Church of Seiros. Reaching an agreement with the Kingdom, he worked tirelessly on the restoration and development of all of Fodlan. Behind his achievements was the knight Gustave, formerly known as Gilbert of the Knights of Seiros, who remained always by the archbishop's side. Byleth came to rely on Gustave for nearly everything. It is said that he continued to call upon Gustave for instruction and advice well into his retirement.