He is a former general who become senator. Leontius was critic of Emperor Nero, who gave an order kill his entire family. After Marius visits his family and after a brief combat session where Marius bests his father and gave Marius the dagger of Damocles. Moments after the barbarians invade his house and killed Septima and Honorata. Both Leontius and Marius rush to the streets of Rome to defend its people against the barbarian invasion. Leontius was mortally wounded by barbarians, and then discovering that the barbarians had prompted him that the invasion to his home was part of Nero's plan to kill his entire family. With his dying breath he told Marius about the plot and Marius swore to avenge his family against Nero.
On all stages, it seems as though he was always stated a good man, 'a man of the people' and a popular senator who wanted authority to be placed back in the hands of the people. He is a man who has learnt from the past, who has taught his son lessons of being a good person to those around and to lead his men with honor, even to the death.