Feast day: February 18
Saint Flavian was the patriarch of Constantinople around the year 446. During his consecration, an advisor to Emperor Theodosius II attempted to extort a gift of gold from Flavian to the Emperor. When Flavian declined, the advisor used a theological heresy to plot against Flavian.
In a synod called by Flavian, the teacher of the heresy, Eutyches, was deposed. (Eutcyches taught that Jesus was fully divine but not fully human.) Eutyches protested this verdict, and the Emperor convoked another Council. Flavian was deposed and exiled, and Eutyches was reinstated. During the sessions of this Council, a mob of monks who supported Eutyches beat Flavian severely. He died shortly afterward from his wounds.
Pope Leo I protested this council as illegal, "a robber synod," and declared its decisions void. The Council of Chalcedon convened in 451, condemned Eutyches, confirmed a letter of Pope Leo I clarifying both the human and divine natures of Christ, and declared Flavian a saint and a martyr.
(Image Siriopomante, public domain, via Wikimedia Commons)