Most of the Indo-Iranian gods were anthropomorphic (human-like), however Verethraghna resembles a wild boar and all these gods were assumed to be immortal. A cosmology evolved and the first creation myth of the Iranians belongs to this period. "The gods created the world in seven stages. First they made the sky of stone, solid like a huge round shell. In the bottom half of this shell they put water. Next they created earth, resting on water like a great flat dish; and then at the center of the earth they fashioned the three animate creations in the form of a single plant, a single animal (The bull) and a single man (Gayo-maretan, 'Mortal Life', Kewmarth in modern Persian). Seventh, they created fire, both visibly and as a vital force. The sun, part of the creation of fire, stood still overhead as if it were always noon. The world was motionless and unchanging, and then the gods offered a triple sacrifice. They crushed the plant, and then slew the bull and the man. From this sacrifice came more plants, animals and humans. The cycle of life was set in motion and death was followed by new life. The sun began to move across the sky to regulate the seasons in accordance with asha (in Zoroastrian literature this day is called the first No Ruz).

The Avesta does not represent the whole of the sacred scriptures of the Parsees. It is supplemented by an extensive Pahlavi literature, consisting in part of translations from the sacred canon and in part of original matter. The most notable Pahlavi works belonging here are the Dinkard (Acts of Religion), dating from the ninth century of the ; Bundahishn, "Original Creation", finished in the eleventh or twelfth century of the , but containing material as old as the Avesta itself, being in part a version of one of the original nasks; the Mainog-i-Khirad (Spirit of Wisdom), a religious conference on questions of , and the Arda Viraf Namak, a sort of Zoroastrian "Divina Commedia", which is especially important because of its account of the Persian concerning the future life. There is also some later Zoroastrian literature in modern Persian, comprising works like the Zartushtnamah (Book of Zoroaster), the Sad-dar (Hundred Doors, or Chapters), the Rivayats (traditional treatises).