Zoroastrianism is named after the Prophet Zarathustra (Zoroaster in Greek), who lived around 1000 BC. It had been the most important religion in the region of Iran for centuries and became the official state religion under Shapur II (309-379). This remained the case throughout the Sasanian period.
According to Zarathustra, the universe was created by Ahura Mazda, who also maintains order in the spirit world. He represents Good in the battle against Evil (personified as Angra Mainyu) and he is assisted by six Holy Immortals (Spenta Mainyu). Amongst other things, they make sure that only the rightful kings of Iran come into possession of the God-given Glory, the khvarenah.
The Sasanian kings always wore a distinctive crown, often bearing the symbol of their favourite yazata or divine being. As the coin inscriptions mention the personal name of the king, it is possible to identify different kings on rock-reliefs and small objects by their crown.
Ardashir I (224-241) wore several different combinations of headgear during his reign: a tall bejewelled hat; a diadem or headband; and a cap with a diadem and silk-covered ball of hair. All these types have on the back the Zoroastrian fire altar and throne. The rock relief pictured here, from Naqsh-i Rustam near Persepolis, southern Iran, shows Ardashir on the left receiving his diadem from Ahura Mazda. The horses trample on the bodies of two defeated enemies: one is the Parthian king Ardavan and the other is Angra Mainyu.
Ardashir was particularly associated with Anahita, the yazata of Fertility and all Waters. Other important yazatas include Mithra, who controls the sun, moon and seasons, and Verethragna or Bahram, the victorious warrior god.