To fight Erebus, they needed to grow stronger. A mysterious guide, "The Archivist," appeared, offering keys to ancient training realms—each tied to a different legacy.
Goku entered the Chamber of Eternal Gravity, where he trained against echoes of Vegeta and Jiren. Naruto meditated in the Temple of Tailed Spirits, awakening a new form: Six Paths Kurama Mode.
Luffy fought illusions of Shanks, Ace, and Kaido to master his own conqueror's will, while Gojo pushed the boundaries of his Limitless to create a new cursed domain.
But training wasn't easy. Each realm tested them mentally—facing regrets, losses, and fears. Goku briefly saw his home planet destroyed again. Naruto relived Jiraiya's death. Gojo felt Geto's final words. Luffy saw Ace die, again and again.
When they emerged, they were reborn—warriors sharper, faster, deadlier.