Complex sentence: The ceremony began with the new Pope descending to the tomb of St. Peter in St. Peter's Basilica and along with the Patriarchs and Major-Archbishops of the Eastern Catholic Churches prayed at the tomb.
Split into simpler sentences: The ceremony began with the new Pope descending to the tomb of St. Peter in St. Peter's Basilica. The pope, along with the Patriarchs and Major-Archbishops of the Eastern Catholic Churches prayed at the tomb.