|“||Reyna and I used to talk about Diocletian. We both kind of idolized the guy as a leader . . . he was a good ruler. He worked his way up from nothing by joining the legion. His parents were former slaves . . . or at least his mom was. Demigods know he was a son of Jupiter - the last demigod to rule Rome.||”|
Diocletian was one of the last pagan Roman Emperors. He was the son of Jupiter, making him the last demigod to rule Rome. During his career, Diocletian became responsible for the deaths of several thousand Christians in his persecution of Christianity. Weakened by illness, Diocletian became the only Emperor to voluntarily abdicate the throne after his defeat at the hands of his nephew, Constantine, whom he had formerly exiled. He lived out his retirement in his palace on the Dalmatian coast.
After his death, Diocletian's ghost was said to haunt his the city of Split. His scepter held the power to reawaken dead Roman legionnaires. It could only be wielded by a child of Hades, and the spirits would only follow an officer of Rome. The scepter became a turning point in the second Giant War, when it was recovered by Jason Grace and Nico di Angelo.
Before the Series
While attending St. Agnes Academy for Colored Children and Indians, Hazel Levesque was taught that Diocletian was a huge villain, responsible for the deaths of several thousand Christians.
On the other hand, decades later, Diocletian was admired by the Roman praetors Jason Grace and Reyna Avila Ramírez-Arellano. The praetors always imagined visiting Diocletian's Palace in Croatia, but they knew that that was impossible. They saw him as one of Rome's greatest rulers.
After receiving a message from Annabeth Chase about the Athena Parthenos, Reyna resigned herself to making the trip to Greece, in hopes of preventing a war. She would head for Diocletian's Palace, believing that if the Seven were in Europe, that was the one place Jason would stop. Fortunately, Jason witnessed all of this in a dream. He made plans with the group to head for Diocletian's Palace.
After the scepter was retrieved by Jason and Greek demigod Nico di Angelo, the latter wielded it in the battle inside the House of Hades. Jason was unable to lead the spirits, as he had just recently defected to Camp Half-Blood. He stepped down as praetor and promoted centurion Frank Zhang to praetor. Frank led the legion of spirits to victory against Gaea's forces, until a combination of demigods, Titans, and Gigantes worked to seal the Doors of Death to prevent anymore enemies from escaping from the depths of Tartarus.
On the way to Long Island, Nico, Reyna,and Coach Hedge shadow travel to Pompeii. There Coach Hedge is possessed by Gaea, and earthen spirits attack Reyna and Nico. Nico tries to control the scepter, and Reyna shouts orders at the ghosts that are summoned from Diocletian's Scepter. The scepter then breaks due to the earthen ghosts were Roman ghosts and the scepter shatters. Reyna tries to control the remnants of the ghosts, but to no avail.