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Metropolitan Peter, also known as Metropolitan Pyotr Mogila, played a prominent role in shaping Alexander Nevsky's religious and political decisions. A highly venerated figure in the Orthodox Church, Metropolitan Peter served as the Metropolitan of Kiev, Halych, and All-Rus' during the mid-17th century. His theological expertise and deep understanding of ecclesiastical matters provided Alexander Nevsky with invaluable guidance, fostering a close relationship marked by mutual trust and profound respect.