Angra Mainyu
Zoroastrianism probably introduced the first idea of the conceptual "devil"; a principle of evil independently existing apart from God. In Zoroastrianism, good and evil derive from two ultimately opposed forces. The force of good is called Ahura Mazda and the "destructive spirit" in Avestan-language called Angra Mainyu. The Middle Persian equivalent is Ahriman. They are in eternal struggle and neither is all-powerful, especially Angra Mainyu is limited to space and time: in the end of time, he will be finally defeated. While Ahura Mazda creates what is good, Angra Mainyu is responsible for every evil and suffering in the world, such as toads and scorpions.