Jiran became Sun-King following the death of his predecessor Hivas. He was described as being a strong leader during his early years as Sun-King. In the early years of his reign, he chose to train the best among his army in the desert by Sunfall, as the conditions were so harsh, it was said the wind could weather armor. The soldiers who survived were made into the kestrels. The first and most infamous of the kestrels was Helis, who would become Jiran's champion.
During the Derangement, the machines became more hostile and attacked humans unprovoked. Under pressure from this crisis, Jiran interpreted the rise of machine aggression as a consequence of the Sun becoming displeased with the Carja, and the only way to stop the machines' aggression was to make human sacrifices to their diety. He then ordered raids against neighboring tribes and villages to take slaves for sacrifices, which became known as the Red Raids. Jiran's atrocities went on for a decade. As the raids progressed, Jiran's sanity crumbled, and eventually began killing his own people for questioning his justification for the Red Raids; he even executed his eldest son and the heir to his throne, Prince Kadaman, for standing up to him and demanding an end to the war.
The death of Kadaman began Jiran's own downfall. His second eldest son, Avad, fled from Meridian with loyal soldiers and made an alliance with the Oseram to oppose Jiran. The combined might of Avad and his Oseram allies led them to successfully attack Meridian itself. With the city falling into chaos, Jiran chose to stay inside his Solarium in the Palace of the Sun. He ordered his trusted kestrels under Helis to take Queen Nasadi and Prince Itamen, his youngest son and sole remaining heir, and flee the holy city. Jiran was soon confronted by Avad, who tried to reason with his father to answer for his crimes honorably. Jiran refused, and Avad was forced to kill him.
After Jiran's death, Avad became the 14th Sun-King and proceeded to undo his father's bloody legacy. Although Jiran's brutal reign was over, his loyalists and their followers (approximately half of the Carja) fled to Sunfall, where they continued to follow his ideology and became the Shadow Carja, declaring themselves the true inheritors of the Sundom. Jiran's youngest son, Itamen, was considered his 'true heir' by the Shadow Carja, but in truth he was only a puppet for Helis and the High Priest Bahavas.
Aside from the Shadow Carja, Jiran is viewed by all the tribes as a homicidal lunatic, universally despised and shunned.
- "He truly thought of himself as a Sun God. His mind was... broken. He believed that blood sacrifice would solve... well, everything."
- ―Jiran's son Avad describing his father
- Jiran is referred to as Jahadin in the Art of Horizon Zero Dawn companion book.