 His mother publicly declared that he was the illegitimate son of Caracalla , therefore due the loyalties of Roman soldiers and senators who had sworn allegiance to Caracalla . After Julia Maesa displayed her wealth to the Third Legion at <unk> they swore allegiance to Elagabalus . At sunrise on 16 May 218 , Publius Valerius Comazon , commander of the legion , declared him emperor . To strengthen his legitimacy through further propaganda , Elagabalus assumed Caracalla 's names , Marcus Aurelius Antoninus . 
