As an Eastern Orthodox Christian, from my experience, there were two different kinds of it:
99.9999999999999999999% of the time it was just some shaman doing something fake and wowing everyone. Nothing really important and just sorta brushed aside. Same thing with curses, divination, you name it.
.000001% of the time (and nearly always in pre-Christian societies) it is seen as angels/demons trying to help out people who have no knowledge of God. Ultimately, it was seen as a kind of precursor to the full Church they would receive once they joined the Orthodox Communion, a kind of mercy to show the people that God still loved them (in the case of, say, Medicine Men in Native American societies) and that he was watching out for them, or an example of the very real evils of Satan.
Also, Icon Worship is a really good way to make everyone hate you at least in those societies, since after the Iconoclast controversy in the 700's and 800's the "veneration not worship" aspect of Icons was extremely pushed. You don't worship the wood, paint, and plaster, you worship Jesus. TBH it's a little bit of a pet peeve to me when people have Icons take the same place as idols do in, say, Babylonian society even though there's no difference.
If you wanna find any kind of info on theories of magic and witchcraft in predominantly Orthodox nations, I'd say research more Greek/Bulgarian/Russian/etc traditions, rather than try to find "Byzantine/Orthodox Witchcraft."