|Weapons/Accessories||Twin Laser Arm Attachments|
|Vehicles and/or Gadgets||None|
|Occupation||Former leader of the Cybermen|
|Residence||19th Century London|
Miss Hartigan was matron of the St Joseph's Workhouse (a job for which she showed great dislike). Some short time prior to Christmas 1851 she met the Cybermen and agreed to help them achieve their goals in return for the promise that she would be heralded when their plans were accomplished. She was also protected by a guard of Cybershades who drove her horse and coach.
When the Reverend Fairchild was killed, Miss Hartigan went to his funeral and set the Cybermen on the mourners, capturing the workhouse owners and killing the rest. The survivors were fitted with earpieces and told to bring their children to the Cybermen's base of operations.
They led the children to a factory by the docks and made them work the machinery to generate electricity so that the CyberKing would rise. Miss Hartigan killed the workhouse owners and the Cyber-Leader told her she would be converted into the CyberKing. She realised they had been planning to betray her the whole time and tried to refuse to be converted but was forced into it.
As the CyberKing
One CyberKing was created by Cybus Cybermen in London in 1851. The Tenth Doctor theorised that the end of the 2009 Dalek invasion of Earth collapsed the walls of the Void, allowing the Cybermen to escape and travel back in time using a stolen Dalek Dimension Vault. Using child labour to generate electricity and produce the ship underneath the River Thames, Mercy Hartigan was made into the CyberKing. She refused to be cyber-converted, and instead used her mental powers to command the entire Cyberman army. The ship rose out of the Thames, with Miss Hartigan and several Cybermen controlling the machine inside the part of the vehicle shaped as a Cyberman mouthpiece, and rampaged across London. Using Jackson Lake's "TARDIS" and an improvised device made from Cyber infostamps, the Doctor severed the link between Hartigan and the Cybermen. The Cybermen and Miss Hartigan were killed in the process, and the CyberKing was transported into the vortex. It was later revealed that this event was not remembered by the people that witnessed it due to the Cracks, which could erase people and events from history.
- She appears as an easter egg character in The Dalek Extermination of Earth.