Ancus Marcius in the context of "Interrex"

Lucius Tarquinius Priscus (Classical Latin: [tarˈkʷɪniʊs ˈpriːskʊs]), or Tarquin the Elder, was the legendary fifth king of Rome and first of its Etruscan dynasty. He reigned for thirty-eight years. Tarquinius expanded Roman power through military conquest and grand architectural constructions. His wife was the prophetess Tanaquil.

Not much is known about the early life of Lucius Tarquinius Priscus. According to Livy, Tarquin came from Etruria. Livy claims that his original Etruscan name was Lucumo, but since lucumo is the latinized form of the Etruscan word lauchume "king", there is reason to believe that his name and title have been confused in the official tradition. After inheriting his father's entire fortune, Lucius attempted to gain a political office. However, he was prohibited from obtaining political office in Tarquinii because of the ethnicity of his father, Demaratus, who came from the Greek city of Corinth. As a result, his wife Tanaquil advised him to relocate to Rome. Legend has it that on his arrival in Rome in a chariot, an eagle took his cap, flew away and then returned it back upon his head. Tanaquil, who was skilled in prophecy, interpreted this as an omen of his future greatness. In Rome, he attained respect through his courtesy. King Ancus Marcius noticed Tarquinius and, by his will, appointed Tarquinius guardian of his own sons.

Tullus Hostilius (Classical Latin: [ˈtʊlːʊs (h)ɔsˈtiːliʊs]; r. 672–640 BC) was the legendary third king of Rome. He succeeded Numa Pompilius and was succeeded by Ancus Marcius. Unlike his predecessor, Tullus was known as a warlike king who, according to the Roman historian Livy, believed the more peaceful nature of his predecessor had weakened Rome. It has been attested that he sought out war and was described in Roman sources as even more warlike than the legendary founder Romulus. Accounts of the death of Tullus Hostilius vary. In the mythological version of events Livy describes, he had angered Jupiter who then killed him with a bolt of lightning. Non-mythological sources on the other hand describe that he died of plague after a rule of 32 years.

Tullus Hostilius was the grandson of Hostus Hostilius, who had fought alongside Romulus and died during the Sabine invasion of Rome. According to Plutarch, when Numa Pompilius died after a reign of forty-three years, his Pontifex Maximus Numa Marcius contended with Tullus Hostilius for the throne, but being defeated, he starved himself to death. Marcius's son, also named Numa Marcius, would serve as praefectus urbi under Tullus, and would be the father of Ancus Marcius, Tullus's successor.