Kartir may have been a eunuch, due to being depicted without a beard in the Sasanian reliefs.
He first appears in historical records in Shapur I's inscription at the Ka'ba-ye Zartosht, which was most likely created between 260–262.
Kartir is the only religious bureaucrat mentioned in the inscription.
Shapur I, a "lukewarm Zoroastrian", was known for his tolerance towards other religions.
Although admiring the teachings of his own religion and encouraging the Zoroastrian clergy, Shapur I let the Jews, Christians, Buddhists, and Hindus to freely practice their religion.
He was also friendly towards the founder of Manichaeism, Mani, whom he allowed to preach freely and even to be an escort in his military expeditions.

Shapur I religious practices seems to have been somewhat unusual, with animal sacrifice being made for the soul of the kings and queens of the Sasanian family.
This presumably seemed "pagan" to Zoroastrian priests.
 Kartir, who "abhorred animal sacrifice" was unable to stop Shapur I from doing them.
Shapur I died in 270, and was succeeded by Hormizd I, who gave Kartir clothes that were worn by the upper class, the cap and belt (kulāf ud kamarband) and appointed him as the chief priest (mowbed).

Hormizd I died the following year; Bahram I, who was never considered a candidate for succession of the throne by his father, ascended the throne with the aid of Kartir, whose authority and influence had greatly increased.
Bahram I then made a settlement with his brother Narseh to give up his entitlement to the throne in return for the governorship of the important frontier province of Armenia, which was constantly the subject of war between the Roman and Sasanian Empires.
Narseh held the title of Vazurg Šāh Arminān ("Great King of Armenia"), which was used by the heir to the throne.
Nevertheless, Narseh still most likely viewed Bahram I as a usurper.
Kartir may have been a eunuch, due to being depicted without a beard in the Sasanian reliefs. He first appears in historical records in Shapur I's inscription at the Ka'ba-ye Zartosht, which was most likely created between 260–262. Kartir is the only religious bureaucrat mentioned in the inscription. Shapur I, a "lukewarm Zoroastrian", was known for his tolerance towards other religions. Although admiring the teachings of his own religion and encouraging the Zoroastrian clergy, Shapur I let the Jews, Christians, Buddhists, and Hindus to freely practice their religion. He was also friendly towards the founder of Manichaeism, Mani, whom he allowed to preach freely and even to be an escort in his military expeditions. 
Shapur I religious practices seems to have been somewhat unusual, with animal sacrifice being made for the soul of the kings and queens of the Sasanian family. This presumably seemed "pagan" to Zoroastrian priests.  Kartir, who "abhorred animal sacrifice" was unable to stop Shapur I from doing them. Shapur I died in 270, and was succeeded by Hormizd I, who gave Kartir clothes that were worn by the upper class, the cap and belt (kulāf ud kamarband) and appointed him as the chief priest (mowbed).
Hormizd I died the following year; Bahram I, who was never considered a candidate for succession of the throne by his father, ascended the throne with the aid of Kartir, whose authority and influence had greatly increased. Bahram I then made a settlement with his brother Narseh to give up his entitlement to the throne in return for the governorship of the important frontier province of Armenia, which was constantly the subject of war between the Roman and Sasanian Empires. Narseh held the title of Vazurg Šāh Arminān ("Great King of Armenia"), which was used by the heir to the throne. Nevertheless, Narseh still most likely viewed Bahram I as a usurper.
Kartir