Relief depicting victory of Darius I over magus Gaumata with inscriptions in three languages, ancient Persian, Elamite and Babylonian, Bisotun $($Unesco World Heritage List, $2006),$ Iran, Achaemenid civilization, $6$th century BC$/$DE AGOSTINI EDITORE$/$ Bridgeman Images

to define the limits of the Persian emperor's authority.

in response to the threat of invasion.

to advertise and celebrate Darius's military victories.

to assert that Darius was the son of Ahura Mazda.