Complex sentence: The Church, once confining itself to only the powers of canon law increasingly appealed to secular powers, and heretics such as the Vaudois, Albigenses, Beghards, Apostolic Brothers, and Luciferians were "treated with cruelty" Lazare, Bernard.
Split into simpler sentences: The Church, once confining itself to only the powers of canon law, increasingly appealed to secular powers. Heretics such as the Vaudois, Albigenses, Beghards, Apostolic Brothers, and Luciferians were thus "treated with cruelty" Lazare, Bernard.