Sun Lamp. The guide on gamefaqs says it's it in the underground Kutomina castle, but I simply can't find the thing.

¦ About the hidden room of the Kutomina palace of the subcontinent

I will explain it on the premise that "I am helping Dragobird."
We distinguish the towers by alphabet.

A is a tower where there is a room of Prince Cruz. There is a switch on the top floor.
B is a tower in the west of A.
C is a tower in the north of B. There is a descent switch of the elevator.
D is a tower in the northeast of C. It is a landmark that there are two treasure boxes on the roof.
E is a tower to the east of D. It is a tower where Dragonbird was caught.
F is a tower in the southeast of E. It is a tower where there is a room to open the door with a "candlestick on fire" (Sun Lamp?).
G is a tower south of F tower.
H is a tower with a dawn room. There is a switch on the top floor.
will do.
It is easy to understand by writing the position of the tower in a diagram on a paper.

The hidden room is on the bottom floor of B tower.
The passage from A tower to B tower and H tower to G tower will rise by turning on the switch on the top floor of A and H (red).
When you descend to the bottom with the elevator of E tower, you are connected to the basement of H tower. I will use this to go to the B tower where there is a hidden room.

First of all, we have to have an elevator in the basement of H tower,
A ? B ? C ? F ? E ? H
Walk around the palace tower clockwise in this order.
If you prepare an elevator in the basement of H tower, turn off the switches in A tower and H tower.
If you lower the rising aisle, a passage to the hidden room will appear in the basement.

Use the elevator in the basement of H tower to get back to B's tower in the reverse direction of the clock.
H ? E ? F ? C ? B
It will be.
After getting off to the bottom floor of the elevator of B tower and proceeding to the right you will reach a small room with 3 treasure chests.