Era
Middle Ages
The Cathedral is the first real dungeon of Chrono Trigger. Frog will join early, and you will also have Lucca in the party. Lucca will be especially useful since the Naga ette and Hench enemies are both highly vulnerable to her Flame Toss Tech.
The Cathedral is divided into two main sections. In the first section, you can head right up the center hall, but there is a lot of good Treasure to find in the outer rooms. In particular, take the right stairway (a notch in the wall) in the northeast room to find the shrine to Magus and two new Accessories.
The second section is a large square. Whichever way you go, the stairs will collapse behind you, so you'll need to work your way all the way around, making sure to hit the skull switches in both side rooms. Once you return to the center room, the spikes will be lowered. Fight your way into the room, grab the Iron Sword, and play the organ to open the path in the northern hallway.
Don't forget to use the save point in the subsequent hallway, because the Boss fight against Yakra follows. This is not a hard fight, but don't use Lucca to attack since Yakra resists magic and likes to counterattack. Frog and Crono's X Strike should be more than a match for him, though. After the fight, you will be automatically returned to Guardia Castle and Frog will leave the party.
The Cathedral is divided into two main sections. In the first section, you can head right up the center hall, but there is a lot of good Treasure to find in the outer rooms. In particular, take the right stairway (a notch in the wall) in the northeast room to find the shrine to Magus and two new Accessories.
The second section is a large square. Whichever way you go, the stairs will collapse behind you, so you'll need to work your way all the way around, making sure to hit the skull switches in both side rooms. Once you return to the center room, the spikes will be lowered. Fight your way into the room, grab the Iron Sword, and play the organ to open the path in the northern hallway.
Don't forget to use the save point in the subsequent hallway, because the Boss fight against Yakra follows. This is not a hard fight, but don't use Lucca to attack since Yakra resists magic and likes to counterattack. Frog and Crono's X Strike should be more than a match for him, though. After the fight, you will be automatically returned to Guardia Castle and Frog will leave the party.