Altos (The Keys of Marinus)

Altos was a young man sent by Arbitan to find the keys to the Conscience of Marinus, but instead became enslaved in the city of Morphoton. After being freed, he accompanied the Doctor and his companions in their search for the keys.

He and Sabetha were romantically involved, a fact which was exploited by the Voord, Yartek by having him hand him one of the Conscience's keys. (DW: The Keys of Marinus)