Elagabalus: the sources and the coins
No emperor has a worse reputation, and no reputation rests on sources as suspect. The coinage tells no scandal: it tells of a religious reform.
A priest of fourteen
Varius Avitus Bassianus was high priest of the sun god of Emesa, in Syria, where the cult was addressed to a conical black stone. Brought to power in 218 by his grandmother Julia Maesa, he had the stone carried to Rome and built it a temple on the Palatine.
He intended to place his god at the summit of the Roman pantheon, above Jupiter. That was a considerable religious break, and it is probably the underlying reason for his murder in 222, at eighteen.
Hostile sources
The excesses reported — the banquets, the rain of petals that smothered the guests, the sexual provocations — come mainly from the Historia Augusta, a late compilation written more than a century after the events and known for inventing documents and anecdotes. Dio Cassius, a contemporary, is hostile but soberer.
This does not mean all of it is false. It means that a serious historian distinguishes what is attested from what is legend, and that Alma-Tadema's painting illustrates a literary tradition, not an established fact.
The evidence of the reverses
The coins, for their part, are contemporary official documents. They show the emperor in priestly dress sacrificing before an altar, with the legends SACERD DEI SOLIS ELAGAB or INVICTVS SACERDOS AVG. Some reverses figure the black stone itself, carried on a quadriga, under the legend SANCT DEO SOLI.
In other words: the only message the regime chose to broadcast widely was religious. That is the best argument for saying the issue was not debauchery but the cult.
Further reading
M. Icks, The Crimes of Elagabalus, London, 2011.
L. de Arrizabalaga y Prado, The Emperor Elagabalus. Fact or Fiction?, Cambridge, 2010.