Az is the demon of lust, greed, and jealousy in Zoroastrianism. She is the female counterpart of Angra Mainyu, the Zoroastrian god of evil and destruction. She was created by the evil god to spoil mankind by twisting their minds with lust, envy, and greed.
During Frashokereti (the Persian end of the world), when mankind becomes immune to Angra Mainyu's filth, Az, who would starve without the indulgence of humans, would pursue her master and swallow him. Angra Mainyu would escape, plead for mercy from Ahura Mazda, the supreme god of good, light, and truth, whom will cast him back into the darkness from whence he came.