Socra

Socra was the Prydonian Chancellor of Pandad IV, and, as such, a member of the High Council of the Time Lords. He was also a member of the Celestial Intervention Agency, and, on the orders of Rassilon, took a vested interest in the Doctor's adventures. (PROSE: The Legacy of Gallifrey)

Biography
By the time he ascended to the position of Chancellor on Lord President Pandad IV's High Council, Socra was a member of the Celestial Intervention Agency, and knew that his Matrix-confined lord, Rassilon, had a special interest in the Doctor, who had acted, consciously or otherwise, as his free agent in the wider universe while the CIA served him on Gallifrey. (PROSE: The Legacy of Gallifrey)

Alongside the councillors Goth and Adelphi, Chancellor Socra (PROSE: The Legacy of Gallifrey) was part of a council of three who tried the Second Doctor on the battleground-planet of the War Lords, eventually condemning him to a force regeneration and exile on Earth. He was also present for the War Lord's trial, and he watched as the War Lord and his guards were dematerialised. He escorted Zoe and Jamie to say goodbye to the Doctor. (TV: The War Games)

Socra was asked by Rassilon to look out for the Third Doctor during his exile on Earth, and convinced President Pandad IV to send another member of the High Council to Earth to warn the Doctor that the Master had escaped their grasp and was now out for revenge. (PROSE: The Legacy of Gallifrey)

At some point, this Time Lord (PROSE: Doctor Who and the Doomsday Weapon) regenerated into a new body. After a report on the Doomsday Weapon went missing from the Time Lords' files, he was part of a group that decided to send the Third Doctor to the planet Uxarieus to investigate. (TV: Colony in Space)

This change of appearance appeared to be brief, however, as Socra had returned to using the body of the incarnation involved in the Doctor's tribunal by the time of the First Omega Crisis. (TV: The Three Doctors) Indeed, Postar the Perfidious apparently thought Socra's change of appearance didn't even merit inclusion within the Scrolls of Gallifrey. (PROSE: The Legacy of Gallifrey)

He was still Chancellor during the First Omega Crisis, when help from the first three incarnations of the Doctor was required. The Chancellor objected to the President's plan to have the Doctor cross his own time stream, citing the First Law of Time. (TV: The Three Doctors) At the end of the crisis, he insisted with the President that the Doctor had earned his freedom. When Pandad IV demanded a more candid explanation, the Chancellor was authorised by Rassilon to reveal the existence of the CIA to him, though Pandad chose not to make it public so as not to weaken the population's faith in the Presidency. (PROSE: The Legacy of Gallifrey)

Later during Pandad's presidency, Socra was eaten alive by one of several giant mice accidentally created by the Rani's experiments, (PROSE: The Legacy of Gallifrey) whose attack also cost the life of Pandad IV's cat and triggered a regeneration in the President himself, (TV: The Mark of the Rani, PROSE: The Legacy of Gallifrey) leading to the Rani leaving Gallifrey and turning renegade. (PROSE: The Legacy of Gallifrey)