Chrono Trigger Jets of Time Randomizer - Magus Castle Walkthrough

Magus Castle is one of the "go-modes" of this game. You need the following: Frog, Bent Sword, Bent Hilt. You forge the masamune at Balthazar's place in 1000AD and then take it and Frog back to 600AD to "open" the sealed cave. That unlocks Magus Castle.