It's not a specific location you can go to, but rather a recurring element throughout the game. You'll encounter it when:
* Traveling between floors: You'll use the spiral staircase to move between different floors of the castle, especially in the early levels where you're exploring the castle.
* During certain quests: Some quests may require you to use the spiral staircase to reach a specific location.
* During duels: The staircase can be a strategic location for duels, offering different vantage points.
Keep in mind that the spiral staircase is a general feature of the castle, not a specific location with a unique name.