St. Mark of Ephesus

Our father among the Saints Mark Evgenikos  Archbishop of Ephesus, was famous for his courageous defense of Orthodoxy at the Council of Florence (1439 A.D.) in spite of the Byzantine emperor John VIII Palaeologus and the "pope" of Rome Eugenius IV. He held Rome to be in schism and heresy for its acceptance of the Filioque clause added to the Nicene-Constantinopolitan Creed and for the claims of the papacy to universal jurisdiction over the Church, and was thus the only Eastern bishop to refuse to sign the decrees of the council. Sometimes he is called "the conscience of Orthodoxy." 

He died peacefully in the year 1444 A.D. On his deathbed, Mark implored Gregory, his disciple, and later Patriarch Gennadius II of Constantinople, to be careful of the snares of the West and to defend Orthodoxy.

For his efforts at the Council of Florence and his defense against: the addition of the Filioque, the primacy of the

Pope, and purgatorial fire purification, the Orthodox Church considers him a Saint, calling him a Pillar of Orthodoxy.

Troparion:

By your profession of faith, O all-praised Mark

The Church has found you to be a zealot for truth.

You fought for the teaching of the Fathers;

You cast down the darkness of boastful pride.

Intercede with Christ God to grant forgiveness to those who honor you! 

Kontakion:

Clothed with invincible armor, O blessed one,

You cast down rebellious pride,

You served as the instrument of the Comforter,

And shone forth as the champion of Orthodoxy.

Therefore we cry to you: "Rejoice, Mark, the boast of the Orthodox!"