Gregory V
When Otto III left Italy for Germany, the situation in Rome remained uncertain. In September 996, a few months after receiving a pardon from Otto III, Crescentius II met with the Archbishop of Piacenza, John Philagathos, a former adviser to the late Empress Theophanu, to devise a plan to depose the newly installed Pope Gregory V. In 997, with the active support of Byzantine Emperor Basil II, Crescentius II led a revolt against Gregory V, deposed him, and installed John Philagathos as Pope John XVI, an antipope, in April 997. Gregory fled to Pavia in northern Italy, held a synod, and excommunicated John.