Arbitan

Arbitan was the Keeper of the Conscience of Marinus and father of Sabetha.

Biography
Arbitan guarded the conscience from the Voord who were trying to capture it. However, he foresaw the need for the conscience to be used and so sent several people out to fetch the four missing keys, including his daughter Sabetha. None of them returned and so, upon the arrival of the First Doctor and his companions, Arbitan blackmailed them into searching for its four missing keys. Shortly after they left, he was killed a Voord who had been hidden nearby. (DW: The Keys of Marinus)