The first era: the World Kings
THE PISHDADIAN DYNASTY
These mythical figures rule over men and animals, and lead the fight against the forces of evil - the Demons (Devs).
Kayumars
Kayumars was the first King of the World. He lived in the mountains and wore a leopard-skin. He was supreme over men and all animals. When Kayumars' beloved son Siamak was killed by demons, Kayumars helped his grandson, Hushang, avenge his death.
He gathered together fairies, leopards and lions, savage wolves and fearless tigers, birds and domestic animals, and this army was led by the intrepid young prince.
Hushang
Hushang, also called Pishdad ("the first created") had farr, and conquered Ahriman and the demons. Kayumars died peacefully knowing his son had been avenged. Hushang ruled for 40 years, establishing justice throughout the world. He discovered how to extract iron from rocks, to draw water from rivers to irrigate the land, to domesticate animals and to build houses. He accidentally also discovered fire, when a rock he threw at a black snake struck sparks. In honour of this discovery, he instituted the festival of Sadeh.

Celebrating Sadeh in Tehran, 2011(photo Farzad j, Public domain, via Wikimedia Commons).
Tahmures
Hushang's son is Tahmures, who during his 30 year reign subjugates the demons, and rides around on Ahriman, who he's turned into a horse. He discovers sheep-shearing, spinning wool for weaving clothes (and carpets), sheep-dogs, falconry, chickens and the use of animals as beasts of burden. When he has the demons at his mercy, they offer to teach him a secret:
They taught the king how to write, and his heart glowed like the sun with this knowledge.
Jamshid
Tahmures' brother, who rules for 600 years, keeping the demons under his control. He invents metal weapons, weaving silk, cotton and flax, dyeing and sewing, mining gold and silver, and bricks, with which to make baths and palaces. He also discovers how to extract jewels and precious metals from the rocks, perfume, and building ships. He divides the people into four classes: those concerned with prayer and worship; the 'lion-warriors'; traders and farmers:
...who work in the fields, receiving no man's thanks, although no one criticises them when it's time to eat.
And finally ' men who work with their hands'
...they are quarrelsome people and their hearts are always filled with anxiety.
Thanks to his farr, everyone is happy. He abolishes evil, old age, illness, envy and bad weather. The demons are ordered to build him a golden throne, which is carried up into the heavens, where he sits shining like the sun, and receiving worship and gifts from all the creatures of the world: to celebrate, he institutes Now Ruz, the New Year Festival. His success makes him arrogant. Under Ahriman's influence, he proclaims himself a god. He loses his farr, and is attacked by the monster Zahhak.
Zahhak
The son of the king of Arabia, who is induced by a demon to murder his virtuous father and seize his throne. The demon then wins his confidence by cooking him a variety of tempting meat dishes (unknown before), and Zahhak allows the demon to kiss his shoulders. Two black snakes grow from the site, which can only be controlled by feeding them on human brains: a demonic plot to destroy the human race. Meanwhile in Iran, Jamshid's subjects rebel against his misrule, and invite Zahhak to become their king. An army of Arabs and Iranians attacks Jamshid, who flees and hides in China for 100 years. But Zahhak finds him, and cuts him in half, to make sure mankind live in terror of him.
After a reign of terror of 1000 years, Kaveh, a blacksmith all of whose sons bar one had been killed to feed Zahhak's serpents, leads a revolt. His leather apron is used as a banner by the rebels. "Kaveh's Apron" became a symbol for the rulers of Iran and their sacred flag.
Feraydun
A descendant of Jamshid, whom Zahhak had dreamed would supplant him. He'd been hidden away, therefore, but now Kaveh produces him to become the rightful king. Zahhak is defeated and imprisoned in a cave on Mount Damavand, loaded with chains, with his body nailed to the rock.

Mount Damavand in winter (photo Hamad Khorramyar)
Peace and prosperity return to the world. In due course, Feraydun decides to divide the world between his three sons: Salm is given the west, Tur is given Turan , Iraj is to rule Iran (Eranshahr). Feraydun's elder sons are not happy with the deal, and together murder Iraj. A long and bitter feud between Turan and Iran will follow. The division of Feraydun's world kingdom brings the first era to an end.