The game is divided into 57 chapters. As the game progresses, Agrippa encounters different types of weapons to use. Weapons break after repeated use. A Salvo is a unique combat technique that Agrippa may perform during battle. Performing multiple different Salvos within a short time period increases the audience's excitement, and increases the chance of them throwing newer, more dangerous weapons to Agrippa for his use.
The frequent acquisition of new weapons from the onlookers is a must, since a player's current weapons have only a limited durability, and so break after a few strikes/blocks. Again, 'Salvo strings' become an essential part of surviving later in the game. Some of them are unique in that they can only be performed in certain events, or against certain foes.
During Octavianus' levels, the player can collect coins that allow the player to purchase special items from the various merchants at the city gates. These items are, mainly, just decorations for Octavianus' room. Buying a certain number of items unlocks special costumes which Octavanianus can wear. Achieving certain ranks in the arena battles (Bronze, Silver, or Gold) on the various difficulty levels will unlock certain secrets like minigames and cheats. Completing an arena battle unlocks it in the Battle Selection menu.
The game's primary protagonist. The tough centurion Agrippa becomes a gladiator in order to avenge his mother, slain by general Decius, and to thwart the execution of his father Vipsanius, who has been framed for the assassination of Julius Caesar by Marcus Brutus. The player controls Agrippa throughout the fighting and racing levels.
The game's secondary protagonist. Octavianus is the delicate nephew of the recently murdered Caesar, and a friend of Agrippa. He seeks to gather evidence to unmask Caesar's true assassin, and to reveal the conspiracy behind the deadly deed. He is controlled during the numerous stealth missions.
Claudia is a freed female gladiator. She is a computer-controlled ally who assists Agrippa during certain levels of the game.
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The premise and story of the game revolves around the murder of Julius Caesar, and its aftermath. The story is progressed through Octavianus' portions in the game.
After the death of Caesar, Antonius ascends to the throne as the new Emperor. Promising to lead Rome with the dignity and brilliance the former Caesar did, he is cheered and loved by everyone.
General Agrippa - after a successful raid against a Barbarian outpost - is told that Julius Caesar has been murdered. Shocked, he returns to the Foro Romano, where he is told that his father, Vipsanius, has been framed for the murder. To make matters worse, his mother has been condemned to death. Agrippa cannot accept this, and decides to free his mother by killing her guards. Before they can escape the city, however, she is killed by General Decius, who then defeats Agrippa in battle. Before he is killed, however, Agrippa is rescued by Claudia, a female gladiator. After they are safely away, she tells him that a tournament is to be held to determine Vipsanius' executioner, and that Decius is to compete in the final round. Knowing he cannot return to Rome a free man, he decides to become a gladiator and compete in the tournament.
Meanwhile, Octavianus decides to look into the matter himself. Through various endeavors into the Roman Senate, he finds out that indeed, Vipsanius is not the true murderer of Caesar. The dying Cicero informs Octavianus that a group of conspirators are the ones responsible for the murder. One by one, select Roman Senators are murdered, leading Octavianus to believe that someone does not want them to talk.
As Agrippa continues to advance in rounds, he learns that his owner, Sextus, has more than his share of secrets. Towards the end of the game, he accepts a proposal from the Egyptian twins Iris and Charmian, whose mistress is hinted to be Cleopatra, to assassinate someone of great importance. He then disappears for a time, only to reappear an assassin. His father, Pompey, was defeated in battle by Caesar's troops, and Sextus wants revenge. Since Octavianus is Caesar's immediate family, and thus true heir to the throne, Sextus goes after him, but is stopped by Claudia. Octavianus is arrested for his snooping by Maecenas, Antonius's secretary, soon after.
During the final, decisive match between Agrippa and Decius, Maecenas reveals to the masses of Rome that Caesar was not killed. Instead, his assassins murdered a double. They were employed by none other than Antonius, who found out that he was not really Caesar's heir. In the ensuing argument, it is revealed to the public that Decius is the Caesar double's true killer. The tournament was articulated by Maecenas in order to reveal the conspiracy and Caesar's true heir to a wide audience. Outraged, Antonius orders Decius to murder Maecenas, Vipsanius, and Octavianus, but Agrippa steps in, and defeats Decius for the final time.
Antonius decides to fight Agrippa himself, but loses. As guards take him away, Sextus and his army climb the walls of the Colosseum and demand Antonius. Agrippa rejoins the Roman army in taking back the streets from Sextus' army, joined by Claudia soon after. As they meet Sextus at the docks, Claudia pleads that he not fight Agrippa, but is knocked away. She regains consciousness just as Agrippa stabs Sextus. Agrippa himself begs him to give up, but before Sextus can respond, Antonius' ship fires at a lighthouse behind Sextus. As it begins to fall over, he begins to reminisce about his early days with Claudia. He calls out to her one more time before the lighthouse falls and crushes him. Agrippa and Claudia mourn his death, and Agrippa decides to go after Antonius along with the Roman navy.
After reaching the flagship, Agrippa battles Antonius, and defeats him. Antonius utters one last laugh before falling into the river dead. When Agrippa and Octavianus return to Rome, they received a hero's welcome. The two find Claudia mourning Sextus on a cliff overlooking the docks. She tells them that she is leaving Rome to travel the world. As she leaves, Agrippa asks her to come back and visit some day. She smiles at him, turns away, and walks off. Octavianus vows to seek the Pax Romana, and Agrippa vows to help him any way he can.
There is a final game revelation after the end credits. Iris and Charmian ask each other if they're ready, and state that it's time to tell their mistress that they've reached the end of the beginning.