Journal:Kingdom Hearts III/Story/Olympus
When Master Yen Sid told Sora he'd need to get his powers back, he suggested visiting a certain friend who had lost all his strength and successfully gotten it back.
Sora knew exactly who Master Yen Sid meant, and followed his heart to Olympus. Yet instead of the familiar Coliseum, he, Donald, and Goofy found themselves on a steep mountain trail. Perhaps less surprisingly, they ran into Hades, god of the Underworld, who released powerful Titans that blew our daring trio clear off the mountain.
Sora, Donald, and Goofy landed in Thebes, where they literally dropped in on just the man they were looking for: the hero Hercules. However, their happy reuninon was cut short when a pack of Heartless appeared and lit the city ablaze. With no time to waste, Herc and Sora split up to rescue any citizens still trapped in the fire.
While searching the city, Sora and friends encountered a few less-than-Greek faces. Maleficent and Pete had come to Olympus in search of a black box, but paid little mind to Sora in his weakened state. More distressingly, Xigbar of Organization XIII seemed to suggest Sora's quest to gather hearts might do more harm than good.
Sora was unnerved, but saving the people of Thebes had to come first.
Just when it seemed as though Tebes was out of danger, dark clouds began to swirl around Mount Olympus: a sign that after eighteen years of plotting, Hades had finally begun his coup. Herc raced ahead to the summit, worried for his father, Zeus, king of the gods.
Sora, Donald, and Goofy hurried after him. Up the mountain they went, sending the Rock Titan for a tumble along the way. Soon they reached the gods' abode and joined the battle for Olympus.
Herc used his godlike strength to free his father, Zeus. A dash of immortal combat and a flash of divine lightning later, Hades and the Titans had been sent packing.
Sora never did get a clear answer about how to reclaim his lost strength, but Herc's off-the-cuff advice stuck with him. It's when we want to help people "with all our heart" that we're most likely to succeed—and that phrase would be Sora's beacon going forward.