* Nicholas is a young boy, the protagonist of the story.
* He is imaginative and adventurous. He gets swept up in the world of the "Lumber Room" and its hidden treasures, creating elaborate stories about the objects he finds.
* He is also mischievous and prone to breaking rules. He is often scolded for his actions, but his resourcefulness and ability to entertain himself lead him to create a world of his own.
* His relationship with his elder brother, Herbert, is complex. Herbert represents authority and is often annoyed by Nicholas's antics. However, Nicholas is somewhat in awe of his brother, especially when Herbert acts as a guide in the "Lumber Room."
* He is deeply affected by the loss of the "Lumber Room," feeling a sense of grief and longing for the lost world he created.
Nicholas's character is a poignant portrait of childhood curiosity, imagination, and the bittersweet nature of growing up. The "Lumber Room" represents a place of freedom and self-discovery for him, and its loss symbolizes the limitations and disappointments that often come with maturity.