The area resembles the disused basement under Alunze, and has the same music. There are three main branches to follow. Two are interconnected in a way that forces you keep going back and forth between them to open more of the other one, and lead to several treasures, including a (cursed) Killer Sword and the powerful, but elemental, Thunder Axe. The other path has the majority of the real puzzles.

One room has a staircase that moves away when approached, but there's a sign on the wall to help.

The key is figuring out how the stairs respond to approaches from each side, and herding them into the tile at the bottom that has only one way out.

There's a sliding platform puzzle later on; each of the platforms in a 3x3 grid can move around, but only if they have an arrow pointing that direction (step on the arrow to move it), and only if there's nothing in the way. You enter at the bottom left, and there are doors in each of the other corners. First of all, take the platform across to the bottom right, and cross some pits with the hook to find....

Shaggy's default name is ぴかぴか (Pikapika), which means sparkle, glitter, or shiny.

Shaggy is a light-elemental capsule monster with low physical stats and high everything else, including GUT, which means it won't chicken out easily. It may be awful at causing damage, but it's also the only capsule monster that can heal party members. The healing starts out weak, but improves as the monster evolves. At higher classes, it also learns some attack magic, which works rather better than its physical attacks.

Back to the dungeon... it's not difficult to reach the door in the top right of the sliding platforms room from here, and pushing four pillars onto the different section of floor is good for a fourth Dragon Egg.

If you've visited the other doors in the order given here, getting to the top left door should be simple enough. On the other side is another puzzle: A 3x3 grid of tiles, with some light and some dark. There's a sign on the wall.

The problem with using the Bomb is that each affects not only the tile where you place it, but also the ones next to it. I don't have an exact solution handy, but if you don't give up, you should get it eventually.

Down another flight of stairs is an amazingly simple puzzle: Push the pillar onto the button to open the door.

Prince Alec and Josef are in the next room, ringed by a section of floor that looks a bit odd. As soon as the party approaches them, the odd-looking floor falls away, leaving them trapped in the middle of the room. "Shudder" starts playing, and Idura appears.

I'm not sure what, if anything テザー (Tezar) is supposed to mean, but it's the spell to warp out of dungeons. They call it "Escape" in the English version.

Idura summons some mummies to attack the party. They're not all that tough.

Idura summons some trolls. They're tougher, but not something Maxim and the others can't deal with. For best results, "kill it with fire!"

Yes, she's talking more informally again. As for what to do... why not just take out Idura? Duh?

A deep voice interrupts.

"The Strongest Man" plays as Heidecker walks into the room

Translating "kisama" as "you" fails to convey the level of disdain and hatred it carries, but I can't think of anything else that would still keep the primary meaning.

He summons a small pack of monsters to surround Heidecker.

Heidecker slaughters the monsters with no apparent effort.

Idura teleports away. Heidecker steps on a switch that connects a bridge to the platform where the others are.

He walks over to the prince.

Heidecker leads Prince Alec and Josef out of the room, then returns to talk to Maxim.

Heidecker leaves.

Heidecker comes back into the room.

Heidecker leaves again.

My guess is she was about to say something like 一人の女として ("for myself as a woman") and go into how they don't appreciate her for herself.