Large, mechanical beings that dominate and control humanity, serving as the primary antagonists of the story. Their true nature and intentions remain largely enigmatic.

Will's cousin and initial rival who joins him on the journey to the White Mountains. He is observant and becomes an important traveling companion despite their contentious relationship.

Will and Henry's clever and inventive companion who joins them on their journey. Known for his analytical mind and innovative ideas, he often helps the group with practical solutions.

The daughter of a noble family who befriends Will and serves as his love interest. She teaches him French and introduces him to aspects of aristocratic life.

A mysterious figure posing as a Vagrant who secretly recruits individuals to join a resistance movement. He plays a pivotal role in inspiring Will to undertake his journey.

Will's older cousin and initial confidant, who shares his interest in resisting the Tripods' control. His transformation after being Capped highlights the changes imposed by the Tripods.