The Church of Crete in the Early Byzantine period was one of the twelve archdioceses of the province of Illyricum under the throne of Rome. After 476, when Rome was conquered by the Visigoths, the Church of Crete was briefly attached to the Patriarchate of Constantinople, only to return to the jurisdiction of the Pope after Justinian’s conquest of Italy. This ecclesiastical status was maintained until 731/2 AD, when the Province of Illyricum was transferred from papal jurisdiction to the Patriarchate of Constantinople.
Mousonios, bishop of Herakleion, is mentioned among the Cretan bishops in the records of the Council of Sardis in 343/344 AD. The same bishop, together with three other Cretan bishops, signed the letter to St Athanasius. A bishop of Herakleioupolis participated with other Cretan hierarchs in the Council of Nicaea in 787 AD. The proximity of Heraklion to the bishopric of Knossos, known as early as 170 AD, and the variations of the name (Heraclea, Herakleioupolis) in ecclesiastical documents have led many scholars to reject the identification of Herakleion with the bishopric. However, the identification is hardly disputed, as the bishop’s name is enlisted between the Cretan bishops of Lampe and Knossos. Unfortunately, the bishops of Crete were not recorded in the lists of the Patriarchate of Constantinople until 731/2 AD. The only information we have is from the acts of the synods, in which the names of the sees are often misspelled because hundreds of bishops took part. Perhaps the proclamation of Herakleion as a bishopric, a short distance from that of Knossos, was due to the fact that it was the birthplace of Evarestos, one of the Ten Holy Martyrs who, together with Zotikos of Knossos, were martyred in Gortyn during the persecution of Decius in 249 AD. According to the letter of the Cretan bishops to Emperor Leo I in 457 AD, the Ten Holy Martyrs were considered the patrons of the Cretan Church.