Upon the assassination of Caracalla in April 217, the Praetorian Prefect, Marcus Opellius Macrinus became the next Roman emperor. To help protect himself and his family, Macrinus exiled the remaining members of the Severan dynasty to their estate in Syria, except Julia Domna, who was forced to stay in Rome, where she starved herself to death. When they arrived in Emesa, Julia Maesa, the grandmother, began plotting with Gannys, the tutor of her eldest grandson, Sextus Varius Avitus Bassianus, to overthrow Macrinus and his son Marcus Opellius Diadumenianus.
Bassianus was born the son of Sextus Varius Marcellus and Julia Soaemias Bassiana in c.203. As part of the plot with Maesa, Soaemias claimed Bassianus was actually the illegitimate son of her cousin, former emperor Caracalla. Being the eldest male heir of the Severans, Soaemias declared Romans loyal to Caracalla needed to swear allegiance to her son. Maesa went to the Legio III Gallica in Raphana to display the wealth of the family, which gained their loyalty. At sunrise, on May 16, 218 AD, the legion commander, Publius Valerius Comazon, declared Bassianus emperor. To help strengthen the claim, Bassianus changed his name to that of Caracalla – Marcus Aurelius Antoninus.
Macrinus responded by sending Ulpius Julianus, his Praetorian prefect, along with what he assumed was enough troops to put down the rebellion. They arrived in Syria and during the conflict, the soldiers switched sides, killed the officers and sent the head of Julianus back to Rome. Macrinus then distributed letters to the Senate claiming Antoninus was a fraud and insane, to which the Senate responded by declaring war on Antoninus and Maesa.
On June 8, 218, during the Battle at Antioch, Legio II Parthica also abandoned Macrinus and Diadumenian and joined the Severan force, led by Gannys. Defeated, Macrinus and Diadumenian fled, Macrinus disguised as a courier, but discovered in Cappadocia and executed, while Diadumenian sought safety with the Parthians, but was caught in Zeugma and also executed. Antoninus declared the victory at Antioch as the beginning of his reign and the Senate confirmed it after receiving promises of amnesty and condemned the reign and laws made by Macrinus. Caracalla and Julia Domna were deified and Julia Maesa and Julia Soaemias were declared Augustae.
Antoninus and his family spent the winter in Bithynia–Nicomedia on the way to Rome and things immediately started to unravel. Antoninus was 14 at the time and was earlier the chief priest of the god Elagabal in Emesa, and brought with him ideas and practices that were very foreign to what the Romans traditionally viewed. Historians vary in their accounts of the emperor going forward, but mostly they are unfavorable. Cassius Dio tells us Gannys was executed on the way to Rome because he was trying to force Antoninus to act and live more according to what would be expected in the capital, and small revolts broke out in various legions.
When Antoninus, his family, and entourage, arrived in Rome, Comazon and other allies who helped the family were given high-level positions. Some senators didn’t agree with the appointments, but it didn’t stop Comazon from being name city prefect three times and consul twice. Soaemias was given the title of Clarissima and Maesa named Mater Castrorum et Senatus and both were the first women allowed in the Senate.
Antoninus brought the worship of Elagabal to Rome and placed the deity even above Jupiter. He was latinized as Deus Sol Invictus and a large, black, conical meteorite from Emesa was placed in the Temple of Jupiter Optimus Maximus before constructing a new temple to Sol Invictus. Each summer solstice there was a parade for Elagabal, which was very popular with the masses because free food was distributed. During the parade, a chariot was driven through the city, the chariot itself adorned with gold and jewels and holding the sacred meteorite from the temple. The chariot was pulled by six white horses, and the reigns held by Antoninus as he ran backwards in front, facing his god. Scarce coins were issued showing the chariot during the festival.
Antoninus further enraged the elites by marrying Julia Aquilia Severa, one of the Vestal Virgins. She was his second wife, Julia Cornelia Paula being the first. He left Aquilia Severa within a year and married Annia Aurelia Faustina, but soon after abandoned her and went back to Severa. He was also supposedly the “wife” of Hierocles, a slave from Caria who became the charioteer for the emperor. The Historia Augusta documents Antoninus also married an athlete named Zoticus from Smyrna in a public ceremony in Rome. Besides the marriages and divorces to five women, of which we only have the names of the three mentioned, and the male relationships, Antoninus also had a room in the palace where he would pose as a harlot and solicit passers-by, who were all hired to play along with his charades. He also offered a large fee for any physician who could successfully change his gender.
By 221, the Praetorians could no longer tolerate the bizarre behavior and customs. Julia Maesa sensed the discomfort and brought in her other daughter, Julia Avita Mamaea and her son, Gessius Bassianus Alexianus, who was 13 at the time. Maesa convinced Antoninus to declare Alexianus as Caesar, who then changed his name to Marcus Aurelius Severus Alexander, but soon after changed his mind and stripped the titles when he realized Alexander was being preferred, and claimed his cousin was near death. The Praetorians rebelled and demanded to see Antoninus and Alexander in their camp, to which they complied on March 11, 222. When they arrived in camp, Alexander was cheered and Antoninus ignored, resulting in Antoninus declaring the arrest and execution of anyone participating in the subordination. Instead, the Praetorians executed Antoninus and Soaemias and elevated Severus Alexander to emperor.
After the beheading of the previous emperor and his mother, and their bodies being dragged through the streets, many of their associates, including Hierocles, were killed or removed. The Emesa stone was sent back to Syria, all of the religious edicts were nullified, women were again barred from Senate meetings and things went back to the way they were. It wasn’t until after his death did Antoninus begin being called “Elagabalus”, which is how we often refer to him today.