Zarek the traitor speaks to Kroton. (COMIC: Throwback: The Soul of a Cyberman)
Zarek was a wealthy businessman on Mondaran who would sell secrets of the resistance to the occupying Cybermen. On one occasion, he sold Pendar out to them as the leader of a resistance movement. Kroton, who was in the room, asked how he could sell out his own kind as he did. Zarek explained that he was like the Cybermen — totally empty on the inside, with no emotions. He left afterwards, suggesting that he would like to be paid for the information that he had given. (COMIC: Throwback: The Soul of a Cyberman