- You may be looking for the slave.
Tarvin was the child of an affair between Erco Sallis and his mistress, Jancis. His parentage was hidden by the pair, but was uncovered by "Lord Sutton", actually the latest incrnation of the Warlord Grayvorn, and he disappeared.
Now going by the name Mattias, he worked together with rebel groups to undermine the Excelis war effort and gain freedom for the city's proles. He was frightened of the Wardens. Encountering the Seventh Doctor shortly after he materialised, he mistook him for a member of the Inner Party. When the Doctor informed him otherwise, he asked him whether he was a spy. He told the Doctor about the state of Excelis, and his fear of the Wardens. He was captured along with the Doctor and numerous rebels when their hideout was raided.
Taken to Grayvorn's laboratory, the Warlord used his soul to create meat puppets. He and the Doctor fled to the TARDIS when Grayvorn initiated the destruction of Artaris, but before they could escape, Grayvorn captured him, preventing the Doctor from saving him. (AUDIO: Excelis Decays)