Ok I'll quote myself from my Imperator Maximus back in 2006...
Surenism: Major religion, named after it's founder Suren in the 10th century AD. Surenism largely descends from Zoroastrianism, incorporating strong Christian, Buddhist and Hinduist elements.
Encyclopedia Italica, 29th edition.
"I profess myself a devotee of Mazda, a follower of his 4 avatars. And Suren has been the last avatar before the end of days."
From the Surenist declaration of faith.
Sureninsm is largely a result of the success of the Persian empire under the Ziebelids. With an empire stretching from the eastern reaches of the Sahara to central Asia and Northern India, Persia is the strongest state on Earth and also perhaps the post religious diverse of all empires of its day. Under the shah of shahs live Christians, both Nestorian and Monophysite, Zoroastrians, Buddhists and Hinduists. With this ongoing religious pot pouri it isn't odd that the four major religions end up influencing each other and Suren is the product of these influences.
The exact origins of Suren are not quite known. Born somewhere in Persian Bactria, around 850, Suren would claim to be Persian and to belonging to the noble family of the same name but it is unknown how true his claims might have been. What is certain is that he would be raised up in a place were Zoroastrianism was being heavily influenced by Buddhism and vice versa and Suren's later teachings would be markedly showing the influences of his raising. After moving to Gundishapur sometime around 870, Suren would start preaching in 880 what to a large extend was a syncretic Zoroastrianism heavily influenced by Buddhism and to a lesser degree by Christianity and Hinduism. According to Suren, Vishnu and the Christian god was but one and the same with Ahura Mazda with Zarathustra, Buddha and Christ having been his 3 avatars on Earth.
Two more avatars were to be, the last of them to come with the end of the world when Ahriman and evil in general would be brought down in the final clash by Ahura Mazda, a concept conveniently similar to Christian, Hindu and even existing Zoroastrian ones. [1] While Suren himself never claimed so, he also did nothing to stop the belief that he was the 4th avatar from spreading and after his death this would become part of the new religion's mythology.
For nearly 20 years Suren preaches from one end of the empire to the other before settling to the academy city of Gundishapur in 902. There he dies 8 years later but not before converting Mark of Beirut, inventor of movable type. This will prove pivotal for the spread of the new religion as under the influence of Mark Surenism becomes the first of the major creeds to see its teachings and scriptures spread by typography. Helped by the generally cosmopolitan state of the Persian empire which while officially Zoroastrian is quite tolerant of the other religions in imperial lands and concepts sufficiently close to these of the other major creeds inside the empire conversion to the new religion proves relatively easy. This is true even among Zoroastrians, the empire's official religion as to them it can be described as no more than one further, and last as Surenists are concerned, evolution of Zoroastrianism. [2]
When Suren himself dies in 910, his creed is still confined to relatively small numbers of adherents in the capital of Ctesiphon, the major cities of the empire, Alexandria, Damascus, Aspadana and Susa as well as the university city of Gundishapur. Over the next 3 generations it spreads rapidly along the Monophysite and Nestorian populations of the empire and finds notable success inside Persia itself although there it is often not much distinguished with mainstream Zoroastrianism, itself influenced by Buddhist and other notions, by its practitioners.
It is in central Asia and Persian controlled India that Surenism finds the most widespread success. Central Asia is of course, Suren's own homeland and where the new religion springs from. In India the egalitarianism of the doctrines coupled with being recognizably close to the prevailing religions in north India, Surenism has widespread appeal along the lower castes of the Indian society gaining ground and converts at a rate making it the primary religion of Persian India by the year 1000.
Beyond the borders of Persia the new religion proves quite less successful. The 4 Roman states are solidly orthodox Christian, with certain dogmatic differences among themselves but still solidly Christian. While Surenists are not outright persecuted any more than the small surviving minority of pagans or Jews they aren't received with any greater warmth than Zoroastrians either given the traditional enmity and on and off war towards Persia. Ethiopia, solidly Christian itself and not particularly friendly to Persia either does not react any better. In central and south India, Persia is the encroaching enemy coming from the north and Surenism threatens the existing social order on top of it. Reaction among the Hindu dominated states is drastic with Surenist missionaries often killed out of hand. But Surenism also has a notable effect on Hinduism itself. Hinduism is already in a state of reform since the late 9th century. [3] Contact with Surenism and reaction to it further accelerates this process. [4] It is only in central Asia that Surenism makes considerable inroads beyond the Persian border and among the Turkish tribes there...
[1] Second coming, last avatar of Vishnu and Peshotan in Vohuman Yasht respectively.
[2] One notes that this TLs Zoroastrianism has already seem one such...evolution so to speak when Mazdakites came to dominate it during the Sassanid collapse and the Khazar takeover.
[3] OTL's Advaita Vedanta.
[4] I model the reaction to the OTL reaction to the spread of Islam in northern India. Although the particulars are going to be different I would expect that coming under pressure Hinduism would react and reform.
. But joking aside, I wonder how the Christian world reacts to this sudden transformation in the middle Eastern political world? Esp. if this revolutionised Turkish-Sepharadi empire goes around conquering and converting as new faiths are wont to do. I can imagine initial focus would be on the east (the Levant, Egypt, Arabia, Persia(?)), So the Austrians and Russians might be initially happy until they realize how dangerous a young & hungry faith right on their doorstep is.
