Initially, the castle represents power and authority. Macbeth, as the Thane of Cawdor and later as the King of Scotland, resides in the castle. The castle is a physical manifestation of his newfound status and the fulfillment of the witches' prophecies. However, as Macbeth becomes consumed by guilt, paranoia, and the consequences of his actions, the castle becomes more than just a physical structure.
The castle becomes a prison for Macbeth. He feels trapped by his crimes and the weight of his guilt. The once-glorious castle now feels like a suffocating place, haunted by the ghosts of Banquo and the other victims of Macbeth's tyranny. The castle walls seem to close in on him, symbolizing the walls he has built around his conscience.
The castle becomes a symbol of Macbeth's deteriorating mental state. As he descends further into madness, the castle becomes a place of chaos and disorder. The once-orderly and majestic structure becomes a reflection of Macbeth's disturbed mind, echoing the internal conflict he is experiencing.
Moreover, the castle's transformation parallels the changes in Macbeth's relationship with Lady Macbeth. At first, they share in the ambition to gain power, but as the story progresses, Lady Macbeth becomes increasingly tormented by their actions. The castle becomes a battleground for their conflicting emotions, and it is in this setting that their relationship fractures and ultimately leads to Lady Macbeth's tragic downfall.
Ultimately, the castle stands as a symbol of both Macbeth's rise and fall. It represents his initial triumph, his descent into darkness, and the inescapable fate that awaits him. The physical changes in the castle mirror Macbeth's psychological and emotional journey, culminating in his downfall and demise.