The Magi were a priest-caste, apparently holding their office by hereditary succession.

They claimed to possess, not only a sacred and mediatorial character, but also supernatural prophetic powers.

They explained omens, expounded dreams, and by means of a certain mysterious manipulation of the barsom, or bundle of twigs, arrived at a knowledge of future events, which they communicated to the pious inquirer.
With such pretensions it was natural that the caste should assume a lofty air, a stately dress, and an entourage of ceremonial magnificence.
Clad in white robes, and bearing Upon their heads tall felt caps, with long lappets at the sides, which concealed the jaw and even the lips, each with his barsom in his hand, they marched in procession to their pynetheia, or fire altars, and standing around them performed for an hour at a time their magical incantations.

The credulous multitude, impressed by sights of this kind, and imposed on by the claims to supernatural power which the Magi advanced, paid them a willing homage; the kings and chiefs consulted them; and when the Arian tribes, pressing westward, came into contact with the races professing the Magian religion, they found a sacerdotal caste all-powerful in most of the Scythic nations.
The original spirit of Zoroastrianism was fierce and exclusive.

The early Iranians looked with contempt and hatred on the creed of their Indian brethren; they abhorred idolatry; and were disinclined to tolerate any religion except that which they had themselves worked out.
But with the lapse of ages this spirit became softened.