Queen Voluptua's lizard, Drak, has taken the Queen and the Fygg into the Plumbed Depths. Jump into the well in the northwest corner of Queen Voluptua's private bathing chamber to pursue the kidnapped Queen and the filched Fygg.
The Plumbed Depths - B1
After you jump into the well, you find yourself in a small chamber with an metal door in the north wall. Walk through the metal door, then head north through the hallway, checking the barrel and pots on the left side of the hallway if you wish. Then go through the opening in the north wall.
Head up the stairs, open the pots on the roof of the small room, then go down the stairs into the room.
Speak to the ghost. It's Aqeus the High Drator (i.e. the hydrator), former King of Gleeba, father of Queen Voluptua! It seems he can't rest in peace because of his regret that he neglected Voluptua, resulting in her rude, selfish personality. He'll ask you to rescue her. Check on the bookshelf next to the king to learn some recipes for Gigasteel weapons. Then exit the room through the door in the south wall.
Go down the stairs to the southwest, then go up to find a red treasure chest that contains an Enchanted Stone.
Go back the way you came, and go north past the left side of the ghost's chamber, walking under the stone bridge, to reach a blue treasure chest and a locked purple door. If you don't have the Magic Key, you will have to go back to the Mirage Mahal, head to the top floor, and walk into the north wall of the dome to reach the chest that contains the Magic Key. Once you have the key, check on the purple door here in the Plumbed Depths to go inside.
The jail cells are locked, but you can go to the left and go down the stairs to find a chest in the north part of the room that contains Mythril Ore. Now go back the way you came, and go east across the small bridge next to King Aqeus's chamber. The path to the north is a dead end, so walk down the stairs south of the small bridge, then go north through the archway. In the north part of this area, you will find a ladder on the wall that leads up to the exit. Go down the stairs to the next floor.
The Plumbed Depths - B2
If you want to open some barrels, go southeast and follow the winding path to find the barrels. Otherwise, go northeast across the narrow stone slab, then follow the winding path. Eventually you will reach some stairs going down to the watery area. Go southeast through the archway and continue following the path. You will pass an archway to the right. Go through to find a couple of blue chests, then go back out to the main path.
Continue northwest. There will be an archway. Go through it to find a red chest that contains a Mini Medal. Go back through the archway and head northeast. There is a ladder leading down into a hole, but first go through the arch to the north to find a red chest that contains a Magic Shield. Then go back down and go down the ladder into the hole.
The Plumbed Depths - B3
You will hear Queen Voluptua calling for help. There are a couple of barrels to the left. The path to the left is blocked, so go around the other way. In the northwest corner, you will find Queen Voluptua and her golden lizard Drak, who is apparently now in love with her. Then you must do battle with Drak, now known as the Grand Lizzier.
The Grand Lizzier
The Grand Lizzier can only do one move per turn. Dragon Slash is effective on him. He often uses Fire Breath and Intimidating Scream, as well as normal physical attacks.
After you defeat the Grand Lizzier, watch the scene. You will receive Fygg number five. Queen Voluptua, after realizing that there are people who care about her, has become a much nicer person.
The next part of the story takes place in another area that you can only reach by boat. Sail north from the Djust Desert, then go east and disembark at the southern coast of the northeast continent. You'll find yourself in the Urdus Marshland. Go east and then north across the bridge, then go northwest and cross the bridge there to reach the Iluugazar Plains. In the center, you will find Batsureg.