Quote from: pyewacket on November 22, 2015, 12:20:57 PM
The two main religions, Zoroastrianism and Manichaeism, were influential from east to west in the pre-Islamic period. Elements of which influenced all the developing monotheisms at the time. Manichaeism was even a brief rival of Christianity when they were replacing Paganism.
There was also (among all the other weird religions that have come and gone) the cult of Mithraism. Mithras was always pictured as a man cutting the throat of a bull, and that image was worshipped as a foundation myth across quite a large section of the world at one time. I don't know if it ever really came close to threatening Christianity as a competing religion but it was quite big at one point in time.