The second time he is seen is during the Senate meeting where he convinces the others into trying not to give Percy, Frank Zhang, and Hazel supplies on their trip, as that is the traditional Roman way. However, Reyna Avila Ramirez-Arellano allows them to use The Pax for the quest.
After the battle against Gaea's giant army, Percy is raised on a shield as the Roman campers chant "Praetor," electing Percy to the position, much to the irritation of Octavian. At the Feast of Fortuna, he gives Percy his tattoo, but whispers to Percy that he hoped it hurt. He later claims after stabbing a stuffed animal that Camp Jupiter will get good luck.
At the senate meeting the following day, Percy informed all of Rome about the existence of Camp Half-Blood and the imminent arrival of the Argo II. Octavian was one of Percy's fiercest opponents at the meeting, claiming that Greeks were Rome's enemies and even accusing Percy of being a spy. He demanded that the Roman's take military action against the Greeks, saying that they should destroy them before they have a chance to land. When Percy says that the Greeks are peaceful and that Jason was on board, Octavian accuses him of lying and once the ship comes into view, he began to scream "Beware Greeks bearing gifts!" He points at Percy accusing him of leading the Greeks to the camp. However, Reyna Avila Ramirez-Arellano says that they will allow them to land, but the Legion forces would be ready if it was a trick. Percy swears on his life that it is not a trick and that he will fight alongside Rome if it is. Octavian, he knows will hold that oath to him.
Octavian is ambitious and power-hungry, willing to use any means from extortion to manipulation in order to achieve his goals. However, he seems to want to protect the camp and advocates a conservative approach when it comes to its affairs. He also believed in the existence of the Greek demigods before it was confirmed by Percy and considers them to be enemies working with Gaea.
Octavian is said to be about eighteen, very skinny with blond hair, crazed eyes, and pale skin who wears a white toga over blue shirt and jeans. He often has a ceremonial knife and stuffed animal on hand. His tattoo is composed of a lyre, the symbol of his ancestor, with SPQR inscribed above seven lines (meaning that he has been at Camp Jupiter since he was eleven).
- Prophecy: Octavian can interpret the will of the gods by reading the stuffing of stuffed animals.
- Manipulation: Octavian is a skilled negotiator as well as manipulator. In front of the senate, Octavian hinted several times that he would be a much better leader than Reyna and that Percy was a traitor.
Hazel openly dislikes Octavian due to his manipulative nature as he is blackmailing her with her past for her to vote for him to become Praetor.
He doesn't have a good relationship with Percy. He doesn't trust him since Percy is a Greek, thinking that the Greeks are working with the forces of Gaea. He is also upset when Percy is elected praetor over himself.
While the two never seem to spend much time together, it is clear that Octavian believes Reyna is not a good leader. He complains that she won't allow a quest to find a book of prophecies that he is obsessed with. He also feels that she has let a power vacuum form during Jason's absence. He also manages to make any unfavorable decision (such as making Frank a Centurion) seem like it was all Reyna's idea and he is following orders.
- Octavian is named after Augustus Caesar: A Roman emperor who was often called Octavian or Octavius and even called a son of Apollo, Octavian's divine ancestor.
- Octavian's name means "eighth" in Latin.
- The Ancient Romans used the entrails from sacrificed animals to determine the advisability of any chosen endeavor and event just as Octavian does with stuffed animals.
- When Percy Jackson first meets him, he states that he reminded him of someone. After Octavian says who he was named after, Percy stills states that he reminds him of someone. The person probably is Luke Castellan since they bear a striking resemblance apart from Luke's scar on his face.
- Octavian is obsessed with the Sibylline Books.
- Although it is never stated how many generations Octavian is from Apollo, his family has been at Camp Jupiter for over a century, so he is at least fourth-generation.