Emperor Early reign Severus Alexander became emperor when he was around 14 years old, making him the youngest emperor in Rome's history, until the accession of Gordian III. Alexander's grandmother Maesa believed that he had more potential to rule and gain support from the Praetorian Guard than her other grandson, the increasingly unpopular emperor Elagabalus. Thus, to preserve her own position, she had Elagabalus adopt the young Alexander and then arranged for Elagabalus' assassination, securing the throne for Alexander. The Roman army hailed Alexander as emperor on 13 March 222, immediately conferring on him the titles of Pater Patriae and Pontifex maximus on the following day. Throughout his life, Alexander relied heavily on guidance from his grandmother, Maesa, before her death in 224, and mother, Julia Mamaea. As a young, immature, and inexperienced adolescent, Alexander knew little about government, warcraft, or the role of ruling over an empire. In time, however, the army came to admire what Jasper Burns refers to as "his simple virtues and moderate behavior, so different from [Elagabalus]". Domestic achievements Under the influence of his mother, Alexander did much to improve the morals and condition of the people, and to enhance the dignity of the state. He employed noted jurists, such as Ulpian, to oversee the administration of justice. His advisers were men like the senator and historian Cassius Dio, and historical sources claimed that with the help of his family, he created a select board of 16 senators, although this claim is sometimes disputed. Some scholars have rejected Herodian's view that Alexander expanded senatorial powers. He also created a municipal council of 14 who assisted the urban prefect in administering the affairs of the 14 districts of Rome. Excessive luxury and extravagance at the imperial court were diminished, and he restored the Baths of Nero in 227 or 229; consequently, they are sometimes also known as the Baths of Alexander after him. He extended the imperial residence at the Horti Lamiani with elaborate buildings and created the Nymphaeum of Alexander (known as the Trophies of Marius), which still stands in the Piazza Vittorio Emanuele. This was the great fountain he built at the end of the Aqua Claudia aqueduct. Upon his accession he reduced the silver purity of the denarius from 46.5% to 43%the actual silver weight dropped from 1.41 grams to 1.30 grams; however, in 229 he revalued the denarius, increasing the silver purity