Tragan was a Naglon and the Vice-Chairman of the Parakon Corporation branch on Earth. He used a mask to disguise his non-human traits.
When the Third Doctor and Sarah Jane Smith investigated the Corporation’s activities, Tragan captured them and forced The Doctor to participate in deadly televised games for the entertainment of the citizens of Parakon, or he would kill Sarah. The Brigadier and his troops freed Sarah and arrested Tragan. (The Paradise of Death)