Angra Mainyu
Zurvan was an innovation analogous to Zoroastrian original doctrine. The prophet Zoroaster preached that the benevolent "Ahura Mazda" (the "Wise Lord"), as the creator God, fashioned both "Spenta Mainyu" (the Holy Spirit), and "Angra Mainyu" (the Aggressive Spirit) who chose to turn evil. These two created Spirits were called twins, one good, one evil. Over the centuries "Ahura Mazda" and his "messenger" the good "Spenta Mainyu" became conflated and identified; hence, the creator "Ahura Mazda" began to be seen as the twin of the evil "Angra Mainyu". It was in this guise that Zoroastrianism became the state religion in Achaemenid Persia. Without fully abandoning dualism, some started to consider "Zurvan" (Time) as the underlying cause of both the benevolent "Ahura Mazda" and the evil "Angra Mainyu". The picture is complicated by very different schools of Zurvanism, and contesting Zoroastrian sects. Also, "Ahura Mazda" was later known as "Ohrmazd", and "Angra Mainyu" became "Ahriman".