This is a strange glitch that forces you back down the stairwell, depending upon a number of circumstances.
Palace of Darkness Stairwell
The glitch can happen when you take the stairwell up to the Big Key, wasting around 10 seconds. There are a couple things that have to happen for this glitch to be armed to activate.
- You have to fall into the basement originating from the south entrance of the room above, and haven't taken damage since mirroring to the entrance.
- You bonk anywhere in this room.
- You walk into the stairwell.
If you know that you accidentally armed this glitch, there is a way to stop it from happening.
- Perform a Keydash into the stairwell, either by lining up with the bottom rail or rubbing against the edge of the doorway as you dash into it.
- When you reach the top of the stairwell, your first movement needs to be either left or right.
- It should now be safe to move downward without being forced back down the stairwell.