Mercy Hartigan
Mercy Hartigan appeared in The Next Doctor (2008 Christmas Special) as the human ally of the Cybermen. She worked in St Joseph’s Workhouse as a matron, though she disliked the job. Mercy met with the Cybermen and agreed to assist them in their plans, as long as she was heralded when they succeeded. Mercy was given the protection of Cybershades, who drove her horse and buggy. At the funeral of Reverend Fairchild, Mercy attended with a number of Cybermen. Under her instructions, they took the owners of other workhouses and killed the others. Those that were kept alive were fitted with the Cyber-earpieces (seen in Series 2) to control the workhouse owners, who were instructed to bring their children to the Cyber factory.
In the factory, Mercy made the children work machinery to generate electricity to allow the Cyberking to rise from the River Thames. Mercy then killed the workhouse owners before being told that she would be converted into the Cyberking. Mercy realised that the Cybermen had intended to betray her all along, and does not willingly convert, but she is ultimately over powered and forced to be the brain of the Cyberking. However, Mercy’s superior mind allowed her to take control of the Cybermen’s technology and killed the Cyber Leader that had forced her to convert. With the Cyber Leader dead, Mercy took control of the Cybermen, and attacked London as the brain of the Cyberking. Mercy was stopped when the Doctor used Infostamps (Cyberman technology) to break the link between her and the Cybermen/Cyberking. Overcome with remorse and horror at what she had become, Mercy destroyed both herself and the Cybermen.