James returns to Sta. Jovita searching for Allison, but his quest is interrupted when the Sphinx suddenly appears and traps construction workers with deadly riddles. As Oppa Rockstar, James rescues them, only to be transported to ancient Thebes, where the Sphinx challenges him with a riddle upon which his freedom depends. In the restored city, James takes the form of Adonis and encounters the infant Euclid and his mother, Myrrha. He witnesses a fierce pankration match and later meets Adonis’ grandfather, who invites him home for supper. After wandering the city through the night, James finally answers the Sphinx’s riddle: “Man,” representing the stages of human life. Defeated, the Sphinx perishes, and Thebes crumbles back into dust.

Princess Ruana reveals to Captain McKinley that her Gentle Waters are actually water elementals whose power is strictly restorative: they can heal the living but cannot harm anyone. This revelation helps ROBO4000 and McKinley realize that the fourth wave of Greek monsters has evaded their sensors because the creatures produce electromagnetic disturbances too weak to detect from long distances. Meanwhile, Oppa Rockstar searches the Mediterranean for Ser Cerulean Arlentis. His search brings him to a Hellenistic museum, which suddenly transforms into ancient Nemea. Within the ruins of a shattered tower, James confronts the legendary Nemean Lion. He initially attacks through illusions and shadows, imitating the cunning of Hercules, but his tricks eventually prove ineffective. Forced to abandon deception, Rockstar faces the monstrous lion directly.

Echidna celebrates what she believes is the acolytes’ defeat, believing Bee Girl has been sent away, Love Fey turned to stone, Spartan fallen, and Oppa Rockstar defeated. Yet Michael is secretly alive, recovering under the care of a faith healer, while a Phoenix appears before the unconscious Rockstar. Elsewhere, Ser Cerulean Arlentis and Cielo reach the Griffin’s mountain vault, where the guardian presents Cerulean with a trial involving enormous weighing scales. Realizing that simply adding treasure will not solve the challenge, Cerulean searches the vault for another solution. Among the countless treasures, he discovers an ordinary paintbrush connected to Sophie’s creativity and her dream of joining her school’s Art Club. He then finds a seashell-shaped podium revealing Aphrodite’s mirror, a relic representing Allison’s aspirations for beauty and stardom. Finally, he discovers a hearth-flame tapestry that comes alive, revealing an ancient Greek family and evoking visions of Roanne’s family and their coastal community.

Cerulean’s search continues when he discovers a lyre buried among the treasure. As he plays it, two passages of Ancient Greek materialize in the air, accompanied by visions of James’s love of music and his close friendship with his boy band, Kaleidoscope. He next finds a sword symbolizing Spartan’s courage and warrior spirit, followed by six busts of Greek scholars surrounding a scroll and quill representing Captain McKinley’s intelligence and strategic mind. With the sixth treasure revealed, all six relics surround Cerulean and transform into individual pieces. The Griffin gives him the seventh and final piece, and when Cerulean joins them together, they form Pandora’s Box. Within the legendary box lies the one thing that remained after the world’s evils were unleashed: hope. Cerulean takes the box aboard Cielo and flies into the heavens, proclaiming it the hope of mankind.

Typhon’s spirit awakens and intercepts Cerulean and Cielo, but the Griffin intervenes long enough for them to escape. Cerulean sends Cielo through a portal to Peregrine Lightyear, then faces Typhon alone. Though Typhon ultimately overpowers him, Cerulean refuses to surrender and entrusts the Star of Vis to Captain McKinley before making his final stand. His last thoughts are carried by divine winds to his mother, Selena, who senses his death and collapses in grief. Ruana and Cielo recover Cerulean’s body and return him to Peregrine Lightyear, where Ruana prepares him respectfully for burial. His funeral is attended by McKinley, Ruana, the robots, Cielo, and Uncle Ronald, honoring the young knight’s sacrifice. Yet the mourning is abruptly followed by another tragedy when Uncle Ronald is struck by the immense power of a nuclear reactor.