Elagabalus (c. 204–222 AD)

He arrived in Rome in 219 AD not as a Roman emperor but as the high priest of a Syrian sun god, wearing eastern robes, performing ritual dances, and carrying a sacred black meteorite he intended to install above Jupiter as the supreme deity of the empire. He was fifteen years old.

His path to power was entirely his grandmother's doing. Julia Maesa, one of the most formidable political operators of the Severan era, orchestrated his proclamation by the eastern legions after Caracalla's assassination - spreading the claim, almost certainly false, that he was Caracalla's illegitimate son. The soldiers believed it, or found it convenient to. Within a year, a teenage Syrian priest was emperor of Rome.

What followed generated some of antiquity's most extreme testimony - behavior so scandalous that even hostile ancient sources seem to struggle to contain it. Modern historians treat much of it with considerable skepticism, noting that the accounts were written after his memory had been formally condemned and that delegitimizing a foreign-influenced emperor served obvious political purposes.

What isn't disputed is that he showed no interest in governing conventionally, that real power rested with his mother and grandmother, and that by 222 AD the Praetorian Guard had decided his younger cousin was a more manageable proposition. He was seventeen. His reign remains one of antiquity's most genuinely strange episodes - and one of its most contested.