This is a Secret room in Return to Dark Castle
To open the door, go to the top right corner of the screen in South Wall 2. There's a switch that can only be reached by climbing a slippery rope. To do that, you need to get the Gauntlets from the top of Giant Tree.
Get the Orb
Main Article: Enemies
Main Article: Items
Spoilers and Hints
- The Acid Eyes can be killed by a Stoneball