Nico summons a zombie driver who takes them where Octavian's legion is stationed. Nico tries to fade into the shadows in order to disable the catapults but almost collapses. Will Solace from Camp Half-Blood shows up and teams up with Nico to finish the sabotage job. Nico and Will make it to the first catapult were Nico has an idea: to alter their trajectories so they would fire at each other. They get to the second catapult but before they can continue sabotaging they get caught by Octavian himself. Octavian tries to convince Nico to come to his side but he refuses. Octavian orders the catapults to be fired at Camp Half-Blood but they had already been sabotaged by others and they blew each other up. Octavian's people had turned against him and sided with Reyna but the people from Camp Half-Blood were ready to attack the Romans. Reyna successfully stops the fight by returning the Athena Parthenos, but Gaea ha already awoken.
All the gods show up to help Jason and his friends. Together they wipeout the giants, but Zeus says that someone has to take the blame for what happened. After arguing over who should take the blame Zeus agrees to transport them to Camp Half-Blood where Gaea is rising. Zeus transported the Argo II to Camp Half-Blood. The demigods land reuniting with Reyna, except for Leo who swears he has a plan. Gaea bursts out of the ground but before she can do anything Leo swoops down on top of Festus, the mechanical dragon. Festus carries Gaea away. The plan was to take Gaea as far away from the ground as possible to suppress her powers, Jason and Piper follow Leo. Jason contains her attacks in a ball of air but Leo tells them that he doesn't need them, he assures them that he has a plan. As Jason and Piper descent Leo ignites an explosion that turns the sky gold.
Nico and Will had pursued Octavian who was determined to shot Gaea with one of the catapults. Octavian did not realize that his robe was tangled into the catapult. Octavian cuts the rope to shoot and he is sent flying into the air and explodes. Gaea had been defeated but they were all mourning Leo's sacrifice. Romans and Greeks celebrate together.
Leo had managed to survive, he had died but the cure brought him back to life. Festus survived too and he flies Leo to Ogygia, where Calypso was waiting. Leo asks Calypso to come with him and leave the island. She agrees, they board Festus and soar into the unknown.
"I am Nico di Angelo, son of Hades. I control the shadows. They do not control me." (Riordan 424)
Nico had almost given his life for this quest. He had been braver than any other character risking his life every tim ehe shadow-jumped to transport the Athena Parthenos. Nico did not jus stand up to the people but he stood up to himself and his own limitations. Nico is willing to accept the things he did in the past but he is not going to allow them to control his future. Nico is a character that takes responsibility of things even if he might not be able to handle them. He was the first demigod to know about the Roman and Greek camps, he had entered tartarus alone to locate the Doors of Death and survived. Nico has gone through so much that he will not accept a predetermined fate."You have proven yourself a true hero." (Riordan 451)

I really liked this book and I do recommend it. It might be long for some people but it is a very easy and entertaining read. I had already read all the books in this series and this one was the last one. I have liked Rick Riordan as an author since I was probably nine years old and I am never disappointed on his works.