The Blood of Olympus recap

In the final book, the seven demigods race to reach Athens and stop Gaea from waking, while Reyna, Nico, and Coach Hedge carry the Athena Parthenos statue across the world to reconcile the Greek and Roman camps before they go to war. Both journeys are hounded by giants and by the ancient hunter Orion. Leo secretly builds a device meant to defeat Gaea and quietly prepares to sacrifice himself, having obtained a means that might, or might not, bring him back. In Athens the giants gather and Gaea begins to rise from the earth. The gods, whose split Greek and Roman personalities have paralyzed them, are freed to help once the two camps are reconciled. In the climactic battle Jason and Piper lift Gaea off the ground into the air, cutting her off from the earth that gives her power, and Leo blasts her with fire, undoing her. Leo appears to die in the explosion but is revived by a physician's cure and flies off on the bronze dragon Festus to keep his promise to Calypso. Gaea is defeated, the camps are at peace, and the surviving heroes return home, with Leo turning up alive at the very end.

Previously: Seven demigods, Greek and Roman, were prophesied to stop the primordial earth goddess Gaea from waking and overthrowing the gods with her giants. To unite the two long-hostile camps, the goddess Hera swapped the heroes Jason and Percy and wiped their memories. Aboard the flying warship Argo II, the crew, Percy, Annabeth, Jason, Piper, Leo, Hazel, and Frank, sailed for the ancient lands to close the Doors of Death, which let Gaea's slain monsters return. Percy and Annabeth survived a passage through Tartarus, the abyss beneath the underworld, and the crew closed the Doors from both sides. To keep the Greek and Roman camps from destroying each other, Nico, the Roman leader Reyna, and the satyr Coach Hedge set out to carry a great statue, the Athena Parthenos, back to Camp Half-Blood as a token of peace. As this final book opens, the crew nears Athens for a last stand against Gaea, while the statue's bearers race to prevent a war between the camps.

The two efforts succeed together. Reyna, Nico, and Coach Hedge deliver the Athena Parthenos to Camp Half-Blood just as the Roman legion is about to attack, and the statue's arrival reconciles the Greek and Roman demigods, ending the threat of war between them. In Athens, Gaea awakens and the giants rise, but the reunited camps and the gods, whose warring Greek and Roman natures are finally settled, join the seven in battle. Jason and Piper seize Gaea and lift her into the sky, severing her from the earth that is the source of her strength, and Leo strikes the helpless goddess with a blast of fire, unmaking her and ending the war. Leo, who had secretly obtained a physician's cure, appears to die in the blast, but the cure revives him, and he flies away on the restored bronze dragon Festus to rescue the immortal Calypso from her hidden island as he had sworn. The prophecy of the seven is fulfilled: Gaea is defeated, the giants are scattered, and the Greek and Roman camps stand united in peace. Percy and Annabeth, having survived Tartarus, look toward an ordinary future together. Nico, having let go of a long-held secret grief, chooses to stay at Camp Half-Blood and make a place among friends. In a closing surprise, Leo returns alive, Calypso at his side, reuniting with the crew who had mourned him.