Jack is an eight-year-old boy with dark brown hair and glasses who naturally gravitates toward logic and facts. He approaches magical adventures with deep caution, preferring to think things through before acting. Armed with his trusty notebook, he meticulously records details and rhymes to help solve puzzles on his journey. His timid nature frequently clashes with the demands of his dangerous surroundings, but his loyalty to his friends pushes him to act bravely.

Annie is an imaginative seven-year-old girl who wears her blond hair in braided pigtails. She embraces fantasy and acts on intuition rather than careful planning. Her boundless optimism and quick thinking often propel the siblings into action when they encounter obstacles. She readily accepts challenges that frighten the adults in Camelot, acting as the catalyst for the desperate rescue mission.

Morgan is a wise, white-haired enchantress who owns the magic tree house that transports Jack and Annie through time. As a longtime resident of Camelot, she maintains a complex friendship with King Arthur. She cares deeply for Jack and Annie, serving as their teacher and providing crucial context about the grim situation before falling victim to a freezing spell.

King Arthur is the stern ruler of Camelot. He carries heavy despair due to a dark wizard's curse that has stripped the joy from his home. Guilt over losing his bravest knights in the Otherworld causes him to forbid all magic from his borders. He is highly protective of his subjects and fiercely opposes sending anyone else into danger.

Merlin is a legendary magician whose history is deeply tied to the kingdom of Camelot. Because King Arthur has strictly forbidden the practice of magic within the castle, Merlin must operate from a distance. He relies on strategic planning and his knowledge of human nature to fight against the dark wizard's curse affecting the land.

Queen Guinevere is the royal consort of Camelot. Dressed in a plain gray robe rather than festive holiday attire, she reflects the gloom that has settled over the cursed kingdom. She sits passively beside her husband, enduring the somber atmosphere of the castle while maintaining a gracious demeanor toward guests.

Sir Lancelot is renowned as one of the oldest and bravest Knights of the Round Table. King Arthur sent him on a desperate mission to the magical Otherworld to find a cure for Camelot's curse. He becomes trapped by the domain's hypnotic dangers, draining his legendary strength and leaving him unable to complete the objective alone.

Sir Galahad is the son of Sir Lancelot and a highly spiritual Knight of the Round Table. He carries a silver cup and accompanies his father on the perilous mission to lift Camelot's curse. Like his companions, he falls victim to the supernatural traps of the Otherworld and requires outside assistance.

Sir Percival is the third brave knight King Arthur sent to the Otherworld. He carries a wooden compass to guide the group's journey but ultimately succumbs to the hypnotic magic of the domain. He represents the physical toll the dangerous quest takes on even the strongest warriors of Camelot.