Crono's party heads to the Northern Ruins in 1000 A.D. but can't get into the Ruins due to Cyrus' ghost. So the party tried entering the Ruins in 600 A.D., but can't because the place is falling apart and is in need of repairs.
They go to nearby Choras in search of a carpenter. While there, they meet Toma, who gives them pop and says to pour it on his grave after he's dead. The party then finds a carpenter but he had lost his tools. So they visit Choras in 1000 A.D. and borrow tools from a lazy carpenter who refuses to work. The party takes the tools back to 600 A.D. and gives them to the carpenter who agrees to repair the Ruins.
After the structure is repaired, the party finds Cyrus' tombstone and Frog pays his respects. Knowing Frog is safe, Cyrus' spirit is released and able to move on to the afterlife. But before he goes, he energizes the Masamune making it more powerful. That's when Masa and Mune appear for a moment, eager to see the new blade in action.
After Cyrus' spirit is freed, the Northern Ruins become known as the Hero's Grave.