Zoroaster developed the presence of spirits, devils and guardians, concepts that can also be observed in Catholicism, Judaism, and Islamism. Zoroastrians utilize the Avesta as their divine book. The Avesta comprises chants, ceremonies, and spells upon beasts. Zoroastrianism interjected the belief that 'there is only one God'. They considered there is only one chief deity, Ahura Mazda, or the Wise Lord.