The Satan of Persia. According to Persian mythology, the ages of the world are divided into periods of 1,000 years. When the cycle of “chiliasms” (1,000-year periods) is complete, the reign of Ormuzd will begin, and men will be all good and all happy; but this event will be preceded by the loosing of Dahak, who will break his chain and fall upon the world, and bring on man the most dreadful calamities. Two prophets will appear to cheer the oppressed, and announce the advent of Ormuzd.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894