Ch'otterai (The Mystery of the Haunted Cottage)

A Ch'otterai was responsible for creating a world of fiction from Martha Jones's mind. The Ch'otterai's ship malfunctioned and exploded. The explosion destroyed the Ch'otterai's physical body, leaving Ch'otterai in a ghost-like state. The Ch'otterai was too weak to leave the spot and decided to create stories. The stories drew in people and the more the people believed, the more powerful the Ch'otterai became. When the people the Ch'otterai attracted attempted to leave the planet of fiction, the Ch'otterai destroyed them.

When Martha Jones and the Tenth Doctor landed on the Ch'otterai's planet, it took on the form of the Troubleseekers series, the oldest books of fiction Martha had read. The Ch'otterai took on the guise of Mr Cotterill, the book's villain, to confront Martha and the Doctor when they began to investigate outside of the bounds of the fictional world. The Ch'otterai offered Martha and the Doctor the chance to become Queen and King of the fictional world, but they declined, and later the Ch'otterai demanded that the Doctor transport the Ch'otterai to the Land of Fiction. Instead, the Doctor trapped the Ch'otterai in the TARDIS and it was destroyed through the TARDIS's imagination. (PROSE: The Mystery of the Haunted Cottage)