Valerius came from an old, powerful Roman family. His grandfather was the commander who tortured and crucified Kyrian of Thrace. Valerius was five years old at that time and was present when Kyrian returned as a Dark-Hunter to take revenge on his killer. His father was a Roman senator who was heartless and cruel. He would stutter whenever he had to talk to his father which made him look very weak in his father's eyes. He would attempt to help Zarek when they were young but would get caught and he was forced to make Zarek's punishments worse by being forced to hurt Zarek more just to prove to his father he wasn't weak. Valerius was an adult when his half-brother Zarek took his act of vengeance on their father.
Valerius became a Roman general by age twenty-two. He led conquests throughout Greece, Gaul and Britannia, but his brothers didn't think he was ruthless enough. They drugged him, raped and murdered his favorite slave Agrippina before his eyes, then killed him as well. Because he had seen Kyrian and Zarek avenge themselves, he knew to cry out to Artemis for retribution. He then slew his own brothers.
Because most Dark-Hunters are Greek, they despise Valerius on principle. Some Dark-Hunters, such as Kyrian and Zoe, hate him especially for the crimes his family members committed against them. His aristocratic, aloof manners don't win him any admirers either.
Valerius was very isolated until he met Tabitha Devereaux, who accidentally stabbed him during a fight with Daimons. As he got to know her, he gradually let down his defenses and fell in love with her. She reclaimed his soul from Artemis via Acheron and restored it to him. Because Tabitha's twin sister Amanda is married to Kyrian, the two men have entered into an uneasy détente. Zarek has also become somewhat less hostile toward Valerius an even, at his wife Astrid's urging, gave him nectar as a wedding gift so that he could be immortal like Tabitha. Astrid also gave him ambrosia so that he would have god powers equal to his half brother.