Originally, the Daevas, together with the Ahuras, were a classification of gods and spirits. In later Persian religion they were degraded to a lesser kind of beings, demons. The word 'devil' is derived from their name.
In ancient Persian mythology they are demons who cause plagues and diseases and who fight every form of religion. They are the male servants (or followers) of Angra Mainyu, also known as Ahriman. The female servants are called the Drugs. ogether they fight Ahuru Mazda (Ormazd) and his Amesha Spentas.