Casp

Matron Casp was the leader of the Sisters of Plenitude. She controlled the experiments on the new humans in the Intensive Care Unit beneath New New York Hospital in the year 5,000,000,023. Casp used the experiments to cure other patients in New New York Hospital, where she was Matron. The hospital had great success in curing patients, but the existence of the new humans was kept a secret, with Casp ordering the immediate incineration of any test subject that showed signs of sentience.

Casp tried to divert the Tenth Doctor from the unit after he questioned the methods used to cure the Duke of Manhattan of Petrifold Regression. However, Cassandra O'Brien, inhabiting the body of Rose Tyler, discovered the unit and led the Doctor to it. After rendering the Doctor unconscious with a noxious "perfume", Cassandra summoned Casp to Intensive Care and demanded money from the Sisterhood in exchange for not informing the NNYPD about their criminal activities. Casp refused and responded to Cassandra's blackmail by unsheathing her claws with a menacing hiss. In response, Cassandra had her servant Chip free the Intensive Care patients. This resulted in the quick death of Casp's colleague Sister Jatt.

Casp placed the hospital under quarantine and then disappeared. She attempted to flee from the infectious patients by climbing up a lift shaft ladder in pursuit of Rose and Cassandra, who was now possessing the Doctor's body instead. She grasped Rose's ankle, and berated them for ruining the Sister's work, to which Cassandra responded by telling her to "go and play with a ball of string". However, when a patient below them grabbed Casp's ankle, spreading its numerous viruses to her immunity-free body, Casp fell from the ladder and plummeted to her death at the bottom of the shaft, screaming all the way down. (TV: New Earth)

Personality
Strict and authoritarian, Casp's role as a charitable administrator for the hospital belied her extremist nature and brutal utilitarian methods. Unlike the Doctor, who valued all life, she did not see the diseased test subjects of Intensive Care in as properly human, and justified the immoral practice of keeping thousands of human clones in perpetual suffering to harvest cures as a necessary evil to preserve the utopian social order of New Earth's human society. To Casp and her fellow Sisters, the diseased clones were merely "flesh" and therefore inferior, though she was fascinated when they proved to be capable of speech. Ironically, she also looked down on the human colonisers of New Earth as "primitive", eventually denouncing the human world as "a sickness".

She was shown to be very proud of the Sisterhood's work and its reputation, maintaining a culture of secrecy about the inner workings of the hospital and resorting to cruel and cunning methods to protect it. She instantly saw the Doctor as a threat when he pressed her on the formula used in the Sisters' medicine, and likewise refused to bow to Cassandra O'Brien's attempts at blackmail. In spite of her cool, polite façade, Casp could be easily provoked when pushed; she took offence at the use of the Doctor's title and turned violent in the face of Cassandra's threats to expose the Sisterhood. When the test-subjects were released into the hospital, Casp held Rose personally reponsible for destroying her order's legacy and attempted to exact revenge by pulling her off a ladder. (TV: New Earth)