Eighth Ecumenical Council
The Eighth Ecumenical Council was a reunion council held at Constantinople in 879-880. This council was originally accepted and fully endorsed by the papacy in Rome (whose legates were present at the behest of Pope John VIII), but later repudiated by Rome in the 11th century, retroactively regarding the robber council of 869-870 to be ecumenical. The council of 879-880 restored St. Photius the Great to his see and anathematized any who altered the Nicene-Constantinopolitan Creed, thus condemning the Filioque.
