Diadumenian, Roman emperor (died 218)

Diadumenian was the son of the Roman emperor Macrinus and served as his co-ruler for a brief time in 218. His mother, Macrinus's wife, is called Nonia Celsa in the unreliable Historia Augusta, though this name may have been fictional. Diadumenian became caesar in May 217, shortly after his father's accession to the imperial throne. Elagabalus, a relative of the recently deceased Caracalla, revolted in May of the following year, and Diadumenian was elevated to co-emperor. After Macrinus was defeated in the Battle of Antioch on 8 June 218, Diadumenian was sent to the court of Artabanus IV of Parthia to ensure his safety; however, he was captured and executed along the way. After his death and that of his father, the Senate declared both of them enemies of Rome and had their names struck from records and their images destroyed, a process known in modern scholarship as damnatio memoriae.