Arbitan

From TARDIS Index File, the free Doctor Who reference.

Arbitan
Also known as:
Race:	Near-Human
Home Planet:	Marinus
Home Era:
Appearances:	DW: The Keys of Marinus
Actor:	George Coulouris

Arbitan was the Keeper of the Conscience of Marinus. He blackmailed the Doctor and his companions into searching for its four missing keys. He was killed by Yartek. (DW: The Keys of Marinus)