Vincent Madrox

 was the head of the Overseers on Agora. He was deathfully afraid of the Cybermen. When the Bronze Knights looked like they were winning against the Cybermen, Madrox sided with them to gain favour. They imprisoned him, but he was released by ArcHivist Hegelia. She wanted to become a Cyberman, but they believed she was a companion of the Sixth Doctor and refused. She used Madrox to run the Cyber-conversion equipment to achieve her goal. After the process was finished, she killed Madrox. (PROSE: Killing Ground)