Seratrix

Seratrix was a military strategist of the Time Lords during the Time war. He is described as one of the top strategists of Gallifrey. However, he developed a belief that the only way to stop the Time was is to make peace with the Daleks.

During the Time War
Seratrix had a belief that no one will survive the Time war, and the only way to stop it is to make peace with the Daleks. With this, he gathered some followers, including Bennus and Arverton. When Cardinal Ollistra found out his beliefs, in order to stop the spread of it, she developed a scheme to kill Seratrix. She gave him the device that would create the Null-zone for him to offer to the Daleks. When the War Doctor went to Keska to save him, Seratrix tried to convince him of his beliefs but failed. He was killed when the Doctor stopped the Daleks from drilling into the core of Keska.