When Hazel Levesque is showing Percy Jackson the layout of Camp Jupiter, she is interrupted by Hannibal as he thundered down the road towards a large, open field. He was wearing a bullet proof vest that said "Elephant" (Percy thinks this obvious) and Hazel says they are getting him ready for the War Games. The Fifth Cohort is placed on the attacking team and Hazel says they get the elephant, but the Fifth always loses.
During the game, Frank Zhang manages to breach the defender's walls and he and Percy take down most of the guards while Hazel rode Hannibal into the fort taking down walls and large doors before breaking into the area with the symbol (like a flag). He is very emotional as well, as he becomes upset if he cannot participate in the war games at camp.
During the battle with Alcyoneus, Frank looks back on all the times he had to take care of Hannibal, and uses his power to transform into an elephant. Hannibal is used later during the battle with Polybotes and his armies. It is noted his vest said "ant," with the rest being torn off during the battle. He becomes friends with Mrs. O'Leary, the hellhound.
He is seen playing with Mrs. O’Leary when Jason and the Greeks arrive at Camp Jupiter.
Between the Series
Hannibal pulls the body of Jason Grace to Temple of Jupiter Optimus Maximus during the son of Jupiter’s funeral. The following night Frank Zhang takes him for a walk in the Field of Mars to get some fresh air since his usual caretaker, Bobby, vanished after the battle.
During the assault, he and the dozen remaining legionnaires defend the Caldecott Tunnel when the emperors demand their surrender. However Frank calls for single combat and they accept. He leaves with the others.
- As an elephant, Hannibal is very strong.
- He has a black bullet-proof Kevlar vest that has the word ELEPHANT written on it, which makes him very hard to injure, but gets damaged and after that it says the word ANT.
- When Frank and Hazel are fighting Alcyoneus, Frank is inspired by his time taking care of Hannibal, and uses his familiarity with him to transform into an elephant.
- Hannibal gets indigestion from peanuts.
- He was named after Hannibal Barca, a Carthaginian general who fought the Romans and in the words of their generals "taught us how to fight" referring to the tactics used. He also used elephants during his campaign against Rome.
- Hannibal the Conqueror used 37 elephants to attack Rome in 203 BC., something considered until now one of the greatest war efforts of history.
- Hannibal (Carthaginian General) is said to be Rome's deadliest enemy.
- He's the only friend of Mrs. O' Leary who is the same size as her and is someone she can "play rough with."