The Fated Hour
Resolve seven histories, claim each character's late-game rewards, and approach the Black Omen in the right era order.
Defeat Son of Sun at the Sun Palace in 2300 A.D. Place the Moon Stone in Sun Keep in 65,000,000 B.C.; in 1000 A.D., trace the missing stone to Porre. To reform the mayor's family line, buy Spiced Jerky in 1000 A.D. and give it freely to his ancestor in 600 A.D. Return the restored Moon Stone to Sun Keep, then bring the charged Sun Stone to Lucca. Rewards include Wondershot and Sun Shades; after Rainbow Shell, Melchior can also forge Rainbow and Prism Spectacles.
Bring Magus for extra dialogue and enter the fort east of Magus's former castle in 600 A.D. Defeat upgraded Slash and Flea, inspect Ozzie's trap room before advancing, and let the cat trigger his final mistake. Open the hidden room for Magus's Doom Scythe, Gloom Helm, Gloom Cape, and a Magic Capsule/Tab.
Get the carpenter's Tools from the Choras inn in 1000 A.D., give them to his ancestor in 600 A.D., then pay the workers in stages to repair walkable rooms. Clear monsters between repairs. Power the sealed chests in 600 A.D. without opening them, collect upgraded forms in 1000 A.D., then return for originals. Visit Cyrus's grave with Frog to upgrade the Masamune.
This route requires the sapling to have been preserved in Zeal. Enter the Sunken Desert in 600 A.D., defeat Retinite, then leave Robo to restore the forest. Retrieve him in 1000 A.D. and attend the campfire. During Lucca's memory sequence, reach the machine and enter the mother's name shown in the room; the event has two outcomes but does not block completion.
Put Robo in the party and enter Geno Dome in 2300 A.D. Use conveyor and charging-station puzzles, guide the two dolls to the door, and confront Mother Brain. Defeat the three Displays that heal her, then finish Mother Brain. Robo receives the Terra Arm and Crisis Arm.
Pour Toma's Pop/Spirits on his grave in 1000 A.D., follow the clue to Giant's Claw in 600 A.D., and defeat Rust Tyranno. Guardia stores the shell. In 1000 A.D., return during the King's trial, collect the Rainbow Shard, expose Yakra XIII, and free the Chancellor with the dropped key. Choose one Prism Dress or three Prism Helms; Sun Stone completion adds Melchior's weapon rewards.
Prepare status protection and Ayla's Charm. For maximum repeatable boss rewards, clear the accessible structure from 1000 A.D. to 600 A.D. to 12,000 B.C.; clearing an earlier version removes later ones. Charm Queen Zeal's hands separately if desired, then defeat the Mammon Machine and Zeal's final form before the Lavos route.