Magism
The adjective "Magian" is from Spengler, but he gives no corresponding noun so I use "Magism" (or, with needless verbosity, "Magianism").
Variants of Magism include Zoroastrianism, Islam.
Spengler also classifies Yahwism ("Judaism") and the original form of Christianity as Magian, but I differ.
Islam arose from the encounter between the long-established (and presumably decadent) Persian empire, and the Koranic iconoclasm brought by its Arabic conquerors.
Further analysis needed.