Introduction
Kay Khosrow is the son of Siyavash and Farangis, born and raised in Turan without knowing his father's fate, who eventually returned to Iran, avenged his father's murder, and became one of the most celebrated and spiritually exalted kings of Ferdowsi's Shahnameh.
This article follows the Zoroastrian and Shahnameh traditions, noting where the older Avestan material and Ferdowsi's later epic differ.
Family
Birth and rescue
Kay Khosrow was born in Turan after his father Siyavash's execution, and Afrasiyab, wary of the child's prophesied destiny, kept a close watch on him. The loyal Turanian vizier Piran Viseh protected the infant and his mother Farangis for years, until the Iranian hero Giv, son of Goudarz, undertook a mission to rescue them and bring them safely to Iran.
Avenging Siyavash
Once established in Iran and eventually crowned king, Kay Khosrow led a long and largely successful campaign of vengeance against Turan and Afrasiyab, his own grandfather, eventually achieving Afrasiyab's death, though the pursuit and capture involved considerable difficulty across several books of the Shahnameh.
A saintly end
Unlike other kings of the epic, Kay Khosrow's reign ends not in death or violent overthrow but in a mystical renunciation: sensing the approach of spiritual corruption even in his own success, he voluntarily gave up his throne, distributed his wealth, and walked into the mountains, where he vanished, apparently ascending directly to a higher spiritual state rather than dying an ordinary death, an ending the Shahnameh treats with particular reverence, marking him as one of its most morally exemplary rulers.