Mercy Hartigan

Mercy Hartigan also known as Miss Hartigan was a human agent of the Cybermen, she assisted them in their attempt to conquer Victorian Britain and ultimately the world.

She was in charge of a sick house but when she met the Cybermen she ended up working for them coming up with unrational ways to serve and assist them. She went to a funeral of a vicar who had donated money to help children in workhouses setting Cybermen on the mourners but capturing the owners of the workhouses.

They led children to a factory by the docks and made them work the mechanics so that the CyberKing would rise. She killed the workhouse owners and the Cyber-Leader decided to convert her into the CyberKing. The Doctor then used a device made from Infostamps to break the link between her and the Cybermen. She then saw what she had become and destroyed both the Cybermen and herself in the process. (DW: The Next Doctor)