The 9th-century Metropolitanate of Doros was centered in the Crimea, but it seems to have had dioceses further afield, as far east as the Caspian coast, but they were probably short-lived, as the Khazars converted to Judaism.
Theophilus, the first known bishop of the Goths, defended the Trinitarian and Orthodox Christological position against the Arians at the First Ecumenical Council in Nicea 325, and signed the Nicene Creed.
The Byzantine Metropolitanate, however, was limited to a remnant of the Roman Crimea (the Bosporan Kingdom), consisting only of the southeastern coastal area of the peninsula.
[6] In its disputed 28th Canon, the Council of Chalcedon in 451 recognized an expansion of the boundaries of the Patriarchate of Constantinople and of its authority over bishops of dioceses "among the barbarians", which has been variously interpreted as referring either to areas outside the Byzantine Empire or to non-Greeks.
Its existence is documented in a list of Byzantine dioceses in a Paris manuscript, dated to the 14th century, published by Carl de Boor in 1891.
[clarification needed] Its continued existence is a matter of doubt, as there are practically no records on it, and it may have been little more than a missionary project with the aim of evangelizing the Khazars, or essentially a diocese in partibus infidelium.
[10] The first extant medieval record which confirms that the Gothic language was still spoken in "Gothia" is the Vita of Saint Cyril, Apostle to the Slavs (also known as Constantine the Philosopher) who went to Crimea to preach the gospel to the Khazars in c. 850.
Many "Crimean Goths" were Greek speakers and many non-Gothic Byzantine citizens were settled in the region called "Gothia" by the government in Constantinople.
Timur Lenk devastated Doros in 1395, but Gothia remained nominally independent for another 80 years, until it finally fell to the Ottoman Empire in 1475.
In 1759, the Ottoman sultan Mustafa III issued a firman confirming the metropolitan's authority "over the Christians dwelling in Caffa, Mankup, Balaclava and Azov" in accordance with custom.