Aydan

Aydan was a guard in the city of Millennius on Marinus and the husband of Kala. He, Kala, and Eyesen conspired to steal one of the keys to the Conscience of Marinus. He was the one who murdered Eprin, framed Ian Chesterton for it, then stole the key and hid it. He was exposed by the Doctor at Ian's trial, but was shot and killed by Kala to prevent him from revealing his accomplices' identities. (DW: The Keys of Marinus)