Councils #14: Lyon Council II, 1274
The Second General Council of Lyons was held by Pope Gregory X, the Patriarchs of Antioch and Constantinople, 15 cardinals, 500 bishops, and more than 1000 other dignitaries. It effected a temporary reunion of the Greek Church with Rome. The word filioque was added to the symbol of Constantinople and means were sought for recovering Palestine from the Turks. It also laid down the rules for papal elections.