To save the Iranian identity, Hakim Abu Al-Qasim Ferdowsi Tusi composed the epic of Shahnameh (book of kings). Due to the indisputable belief of people in mythology in his time, Ferdowsi transformed the myth to epic by combining the former with pre- and post-Islam Zoroastrian and non- Zoroastrian texts which led to the creation of Shahnameh. Accordingly, Shahnameh is not just an exclusive report of Iranian beliefs and rites before the advent of Islam. The present article seeks to compare and contrast Shahnameh, Avesta and Pahlavi texts in terms of their arguments about the characteristics of Ahriman and his relationship with Ohrmazd and the universe. To this end, Ferdowsi’s depiction of the nature and attributes of demons, their relation with Ohrmazd and His creations, how to struggle with them and the characteristics of three main demons (i.e. envy, greed, and wrath) are carefully compared and contrasted with ancient Zoroastrian texts. The similarities and differences of these texts are then clarified. This study suggests that, Ahriman and demons have lost their old status in Shahnameh, to the extent of extreme reduction of their influence and power in the world. They have thus approached their inferior status assumed in Islamic texts and culture.